Recommended Books and Products
The following book and product recommendations are not only here to make me incredibly rich (the lump sum of all my amazon referal orders so far being 2.70 Dollars in 3 years), they really helped me in my job and with my career. Furthermore, they are fun to read and save you a lot of time when developing web sites.
DHTML Utopia: Modern Web Design

Stuart Langridge has delivered a wonderful, up-to-date book on DOM scripting. If you want to develop modern JavaScript and you don't feel like scanning through dozens of confusing tutorials and mail threads, this is a good place to start. It does require a certain JavaScript knowledge and is good for developers, pure designers might have a hard time following it.
Web Standards Solutions

Dan Cederholm's book is a hands-on example book showing you how to solve different design and markup problems with web standards. It does not rave on for hours about the importance of web standards, but shows how to use them. If you want to have a handy "how do I do that in HTML and CSS?" reference, this is it.
Don't make me think!

Steve Krug's book is a very easy and quick to read guide on basic usability. It should be read by anyone who designs web sites. Krug explains how basic usability works, how you can avoid confusing your visitors and gives examples what worked for others. Included is also a guide to low cost usability testing. You can finish the book on a long train ride and save hours of development with the wrong focus.
Designing with Web Standards

This gem by Jeffrey Zeldman should be on the bookshelf of any interaction designer. Quite straight to the point and rooted in real life, it explains how you can safe time and money by developing web sites using standards for markup. It is a practical book, explaining how to use XHTML and CSS and why we never really bothered to take the standards seriously.
Building Accessible Websites

Joe Clark is an accessibility guru with a lot of years expertise in the field. This book, which also comes on a CD (handy if you are on the move a lot) explains what accessibility is and what it means for websites. It is a no-nonsense approach describing each element of web design and three levels of how to increase accessibility in each of them. If you are confused by accessibility requirements, this is a very good start.
CSS - The Definitive Guide

Eric Meyer is one of the leading CSS experts, and this reference book, albeit a bit dated, is still a mandatory help for anyone who wants to use CSS seriously and not waste hours on end trying to find out why some colour or padding does not get applied.
The PHP Pocket Reference

As handy as the PHP manual is, from time to time you like to have a book in your hands to leaf through. The PHP pocket reference has been of remarkable help to me when working on client sites without internet access.
The PHP Cookbook (Version 4)

The O'Reilly cookbook series has always been one of my favourites. This book of the series is no exception. Instead of evangelising about a technique or product, it explains how to solve different problems using PHP. For me, a much quicker and more interesting way to learn.
The PHP Cookbook (Version 5)

This book is much like the Safari cookbook. The only difference is that it covers PHP5 and not only PHP4. While the Safari book is a great helper in maintaining and fixing older products, this one gets you ready for the much cleaner, OO future of PHP.
Son of web pages that suck

I avoided Vincent Flander's books and publications, as I don't consider pointing out errors very productive. However, years of frustration talking clients out of bad ideas made me reconsider and I ordered a copy of this book, after reading the excellent the biggest web design mistakes of 2004 article on his web site. This book takes a lighthearted approach to web design, showing bad examples and explaing why they are bad. If you are an inexperienced web designer, it can prevent you from doing a lot of useless work.

