Jenifer Tidwell collected lots of patterns and techniques that are useful in User Interface Design.
Each of these patterns (which are more general) and techniques (more specific) are intended to help you solve design problems. They’re common problems, and there’s no point in reinventing the wheel every time you need, say, a sortable table — plenty of folks have already done it, and learned how to do it well. Some of that knowledge is written up here, in an easily-digestible format.
This web site is becoming a book! “Designing Interfaces: Patterns for Effective Interaction Design” will be published by O’Reilly Media in late 2005.