Smashing Magazine recently posted a an article on 35 (Really) Incredible Free Icon Sets. There's a number of sets I haven't seen. The one that immediately caught my eye was pinvoke's PI Diagona Pack.
It comes with 200 unique icons in two different sizes (10x10 and 16x16.) It has a similar look to the famfamfam set of icons called Silk. Here's what the icons look like:
It seems the pinvoke site's getting a lot of downloads at the moment, but I was able to find a mirror of the pi_diagona_pack.zip file.