As those of us who have attempted to design good icons for our apps know, icon design is a genuine graphic arts specialty. I'm looking for any particularly good libraries of icons (or small JPEGs, bitmaps, etc.) that I can incorporate into my app. I'd also like to find a good graphic artist (preferably in the Washington, D.C. area) who specializes in creating these tiny works of art.

Anybody got any good leads...?