Here’s a great article by Christian Holst on an frequent need: designing country selectors. What I love most is that he’s gone beyond describing the challenges, to designing a working solution—which he then makes open source! You can try out his redesigned country selector and download the jQuery plugin.
Pattern Tap is a showcase of web design, uh, patterns. I promise it’s not a CSS link farm. Just close to it.
Information Design Patterns provides a comprehensive and rich resource. via (The Sweeting)
Patterns of Interaction design: a collection of popular patterns from language selectors, searching, and date pickers. Compiled by Martijn van Welie, Design Director of Satama Netherlands.