nerdcereal.com

This is an open source set of free icons, licensed under the creative commons attribution 2.5. They’re downright sexy, if you’re into that sort of thing. (Did I just call icons sexy?) Don’t waste your time trying to make your own, because it will take too long and won’t look as good as these puppies.

Silk icons are perfect for any web app and make your site look professional and more usable. I haven’t seen them anywhere else but would wager that they will become a staple on most open source web applications.