Luke Wroblewski
LukeW Ideation + Design provides resources for mobile and Web product design and strategy including presentations, workshops, articles, books and more on usability, interaction design and visual design.
Mockups To Go
A user-contributed collection of ready-to-use UI components and design patterns built using Balsamiq Mockups.
HYBRIDWORKS
HYBRIDWORKS,inc. - Official Web Site
AJAX Activity indicators | Animated GIFs designed to indicate your site is doing something
A collection of royalty-free animated GIF icons to use when your web application is loading