These books have been very helpful to me. They range from hard-core technical books to fluffy (but useful) design books. All of them have their place. The biggest mistake that newbies make is to equate knowledge of a tool with the ability to design. Graphic design is both an art and a discipline, and the fundamental principles are the same, whether you are designing a Web page, creating a print magazine ad, or designing a user interface for a program or Web site. A good understanding of those principles will enable you create qualitatively better sites!

• HTML for the World Wide Web • Elizabeth Castro • Classic reference book on HTML, CSS, the DOM, and Javascript. This is one of the class textbooks.
• Creating a Web Page with HTML • Elizabeth Castro • Project-oriented tutorial. This is also one of the class textbooks.
• 250 HTML and Web Design Secrets • Molly Holzschlag • While not an introductory text, this book will make anybody better by applying many of the principles and tips in here.
• Bulletproof Web Design • Dan Cederholm • Subtitled "Improving flexibility and protecting against worst-case scenarios with XHTML and CSS."
• Web Standards Solutions: The Markup and Style Handbook • Dan Cederholm • Very standards-oriented approach to using CSS.
• CSS Mastery: Advanced Web Standards Solutions • Andy Budd • This is one of the best books I've read about advanced use of CSS. Budd is an excellent writer, and the material is top-notch. This not a beginning guide to CSS!
• Blog Design Solutions • Andy Budd, Simon Collison, Chris Davis, Michael Heilemann, John Oxton, David Powers, Richard Rutter, Phil Sherry • This book specifically talks about building blogs, in general and in particular for WordPress, Movable Type, Expression Engine, and Text Pattern. It also shows you how to write your own blogging system. This book requires knowledge of PHP and MySQL, on top of HTML and CSS. If you want to be hacking blogs, though, this is an excellent start.
• Eric Meyer on CSS • Eric Meyer • Subtitled "Mastering the Language of Web Design", this example-based book will improve your ability to use CSS effectively. Eric is an excellent writer with a superb grasp of the material.
• Don't Make Me Think • Steve Krug • This is more about design principles than anything. The basic idea is that you design your sites so that the target audience knows and expects what to do without having to explain or flail around.
• XML for the World Wide Web • Elizabeth Castro • A good introduction to XML.
• Designing CSS Web Pages • Christopher Schmitt • An excellent introduction to using Cascading Style Sheets (CSS) to design Web pages.
• The Zen of CSS Design • Dave Shea and Molly Holzschlag • In-depth examination of some of the superb examples from the CSS Zen Garden.
• The Art & Science of Web Design • Jeffrey Veen • Thorough and well-written.
• Web Redesign 2.0: Workflow That Works • Kelly Goto and Emily Cotler • An excellent design book, aimed at site redesign -- but also useful for the first time. Very few books actually teach good processes, and this is one of the few.
• Site-Seeing: A visual Approach to Web Usability • Luke Wroblewski • A superb design book.
• Design Whys: Designing Web Sites That Sell • Shayne Bowman and Chris Willis • Well-illustrated and well-written guide to building sites for other people.
• The Design of Sites • Douglas Van Duyne, James Landay, and Jason Hong • Subtitled "Patterns, Principles, and Processes for Crafting a Customer-Centered Web Experience", this is a highly technical approach to Web design, based on the idea of "patterns" in programming. This is not for the weak of stomach!
• Designing Web Usability • Jakob Nielsen • This is an excellent computer science reference book about usability in Web design. Nielsen is one of the top experts in usability.
• DHTML and CSS for the World Wide Web • Jason Teague • Example-based book about using Javascript and the DOM.
• DHTML and CSS Advanced • Jason Teague • More advanced book about using Javascript and the DOM.
• Dynamic HTML, The Definitive Reference • Danny Goodman • This has all the nuts and bolts of Javascript and the DOM for programmers.
• Foundations of AJAX • Ryan Asleson and Nathaniel Schutta • An advanced book on AJAX for programmers.
• PHP for the World Wide Web • Larry Ullman • Excellent first book for learning PHP, with some coverage of MySQL.
• The Elements of Typographic Style • Robert Bringhurst • A definitive text about typography, which is one of the great frustrations of the Web because of the lack of cross-platform font support. You'll understand it better, and your designs will be better for having assimilated this book. That being said, it is dense and extremely detailed.
• Layout Index • Jim Krause • Hundreds of sample layouts -- a great way to "write that first sentence" of your design.
• Graphic Design Cookbook • Leonard Koren and R. Wippo Meckler • Another excellent source with hundreds of layout examples of all kinds.
• PANTONE Guide to Communicating with Color • Leatrice Eiseman • Filled with color palettes for print applications, grouped by themes. Lots of good information about color perception, and color combinations that can easily be adapted to the Web.
• The Visual Display of Quantitative Information • Edward Tufte • This is the first of a series of books by Tufte. A superb writer, Tufte writes about how to display information in all forms. His choice of examples is superb -- these books are a pleasure to flip through, even if you learn nothing! Tufte also coined the term chart junk for all of the unnecessary elements that get larded onto designs.