Over the years, I've read or been recommended a number of books which are essential reading for professional web developers. I've compiled the list of books below to help the community find a comprehensive list of good books that can help them be better coders. 

<h3>JavaScript</h3>

<a href="http://www.amazon.com/gp/product/047022780X?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=047022780X">Professional JavaScript for Web Developers</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=047022780X" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - My new favorite book. Almost 1,000 pages of VERY detailed JavaScript information. Written by Nicholas Zakas, Yahoo! Principal Front-end Engineer for Yahoo!'s home page and recommended by the YUI team as well. BUY THIS BOOK!

<a href="http://www.amazon.com/gp/product/0596101996?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0596101996">JavaScript: The Definitive Guide</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0596101996" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Considered the Bible of JavaScript for its thorough coverage of JavaScript. You need to have this in your library, even as a reference.

<a href="http://www.amazon.com/gp/product/1590595335?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1590595335">DOM Scripting: Web Design with JavaScript and the Document Object Model</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1590595335" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - This is a good book to get you familiar with the DOM. 

<a href="http://www.amazon.com/gp/product/1590598563?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1590598563">AdvancED DOM Scripting: Dynamic Web Design Techniques</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1590598563" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> 

<a href="http://www.amazon.com/gp/product/1590596803?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1590596803">Beginning JavaScript with DOM Scripting and Ajax: From Novice to Professional</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1590596803" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - The book by Christian Heilmann that really got me past the initial hump of plain 'ole JavaScript. His writing style is awesome.

<a href="http://www.amazon.com/gp/product/1847194141?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1847194141">Object-Oriented JavaScript: Create scalable, reusable high-quality JavaScript applications and libraries</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1847194141" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - JUST BUY THIS BOOK! Stoyan did a great job of outlining OOJS principles and it's been incredibly valuable.

<a href="http://www.amazon.com/gp/product/0596517742?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0596517742">JavaScript: The Good Parts</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0596517742" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - It's certainly a good book and I would recommend reading it after one of the more intro books like JS for Web Developer by Nicholas Zakas.

<a href="http://www.amazon.com/gp/product/1847196705?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1847196705">Learning jQuery 1.3</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1847196705" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - While covering jQuery v1.3, the techniques discussed are still useful and I still recommend the book highly.

<a href="http://www.amazon.com/gp/product/1590597273?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1590597273">Pro JavaScript Techniques</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1590597273" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - John Resig's famous book on advanced JS techniques.

<a href="http://www.amazon.com/gp/product/193398869X?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=193398869X">Secrets of the JavaScript Ninja</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=193398869X" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Still not out but considering that John Resig is that author, it's sure to be great.

<a href="http://www.amazon.com/gp/product/0321423305?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0321423305">ppk on JavaScript, 1/e</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0321423305" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - One of the first books I picked up and great overview of the language.

<a href="http://www.amazon.com/gp/product/1590597648?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1590597648">Accelerated DOM Scripting with Ajax, APIs, and Libraries</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1590597648" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />

<a href="http://www.amazon.com/gp/product/0321491939?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0321491939">Ajax Security</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0321491939" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Billy Hoffman is the man when it comes to Ajax security and this books shows why.

<a href="http://www.amazon.com/gp/product/0596159773?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0596159773">jQuery Cookbook: Solutions & Examples for jQuery Developers (Animal Guide)</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0596159773" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Tips & techniques from the jQuery team rolled up in a cookbook style. You can't go wrong.

<a href="http://www.amazon.com/gp/product/1935182323?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1935182323">jQuery in Action, Second Edition</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1935182323" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - This is now updated for jQuery v1.4.x as well as jQuery UI 1.8.x. Definitely a must-have for jQuery developers

<a href="http://jqueryenlightenment.com/">jQuery Enlightenment</a> - Cody Lindley did an amazing job in outlining the best jQuery techniques in this self-published book. Totally worth the price.

<h3>HTML & CSS</h3>

<a href="http://www.amazon.com/gp/product/1430219203?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1430219203">Web Standards Solutions: The Markup and Style Handbook, Special Edition</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1430219203" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />

<a href="http://www.amazon.com/gp/product/0321509021?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0321509021">Bulletproof Web Design: Improving flexibility and protecting against worst-case scenarios with XHTML and CSS (2nd Edition)</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0321509021" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> 

<a href="http://www.sitepoint.com/books/cssdesign1/?SID=82b54f50488243b44b6b9c7acb10731a">The Art & Science Of CSS</a> - This is one of Sitepoint's best CSS books. Loved it.

<a href="http://www.sitepoint.com/books/css2/?SID=82b54f50488243b44b6b9c7acb10731a">HTML Utopia: Designing Without Tables Using CSS, 2nd Edition</a> - Not being a designer, I thought this book was a tremendous help in understanding how to better design sites.

<a href="http://www.amazon.com/gp/product/1600330045?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=1600330045">Head First HTML with CSS & XHTML</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=1600330045" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - This has been my goto book for some time. The Head First books are just so great at breaking down topics in easy to understand ways and this book is no exception.

<a href="http://www.amazon.com/gp/product/0321687299?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0321687299">Introducing HTML5 (Voices That Matter)</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0321687299" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Going to get this soon mainly because it's written by Remy Sharp and Bruce Lawson whom I respect tremendously, especially for their HTML5 & CSS3 savvy.

<a href="http://books.alistapart.com/product/html5-for-web-designers">HTML5 For Web Designers</a>  - Just got this on 7/19/10. Need to read it by it's by Jeremy Keith and he rocks.

<a href="http://www.amazon.com/gp/product/059615593X?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=059615593X">CSS Cookbook, 3rd Edition (Animal Guide)</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=059615593X" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Just picked this up on a recommendation.

<a href="http://www.amazon.com/gp/product/0596802447?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0596802447">CSS: The Missing Manual</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0596802447" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - I keep hearing rave reviews about this book all over the place.

<h3>Site Performance & Enhancement</h3>

<a href="http://www.amazon.com/gp/product/0596529309?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0596529309">High Performance Web Sites: Essential Knowledge for Front-End Engineers</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0596529309" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Steve Souders is the performance guru and if you want your apps to perform better, get this book and the one right below this one.

<a href="http://www.amazon.com/gp/product/0596522304?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0596522304">Even Faster Web Sites: Performance Best Practices for Web Developers</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0596522304" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />

<a href="http://www.amazon.com/gp/product/059680279X?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=059680279X">High Performance JavaScript (Build Faster Web Application Interfaces)</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=059680279X" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> - Again, another great book by Nicholas Zakas which outlines very important performance techniques for JavaScript applications. 

<a href="http://www.amazon.com/gp/product/0321658884?ie=UTF8&tag=rebasbl-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0321658884">Designing with Progressive Enhancement: Building the Web that Works for Everyone</a><img src="http://www.assoc-amazon.com/e/ir?t=rebasbl-20&l=as2&o=1&a=0321658884" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />

This is certainly not all inclusive and I'm sure there are other books out there that have been great. If you feel very passionate about a specific title, let me know via the comments and I'll check it out.