Several weeks ago I took a usability class here at Microsoft. Usability, of course, is very important at all levels here at Microsoft and much effort goes into making sure our products are usable by their intended users. Honestly, though, I came away with mixed reviews of the class, which was more about the usability process than about usability itself. However one gem that I came away with was a reading list to follow up on. Our admin was kind enough to order us the books on the list and I started whittling away at them over the weekend. I would highly recommend the following books for anyone that works on a software project (regardless whether it is a client or a server app and regardless whether it ships or not).
Don't Make Me Think: A Common Sense Approach to Web Usability, 2nd Edition by Steve Krug (Paperback - Aug 18, 2005)
I finished this book over the weekend. It is very short and can be finished in a few hours but also very helpful. Very soon I plan to incoporate many of the principles in this book to significantly change my wife's real estate web site, which admittedly is not very usable right now.
Designing for Interaction: Creating Smart Applications and Clever Devices (VOICES) by Dan Saffer (Paperback - Jul 18, 2006)
I'm close to finishing this book and it is very handy for creating designs that people love. The information about type faces and fonts I found very helpful, as is the details about the interaction design process. Most companies and groups do not have interaction designers, so this book is very helpful to those who need to pitch in.
The remaining books I have not yet started but will soon.
Paper Prototyping: The Fast and Easy Way to Design and Refine User Interfaces (Interactive Technologies) by Carolyn Snyder (Paperback - April 2, 2003)
Designing Visual Interfaces: Communication Oriented Techniques by Kevin Mullet and Darrell Sano (Paperback - Dec 5, 1994)
Creating Breakthrough Products: Innovation from Product Planning to Program Approval by Jonathan Cagan and Craig M. Vogel (Hardcover - Jan 15, 2002)