I was looking for the icons for one of my sites that I could use (for free of course) and came by this pack from lullabot.com. The attached file contain more than 100 icons.

This icons pack is licensed under the General Public License, which means you allowed to use these icons for any purpose... "The GNU General Public License is a free, copyleft license for software and other kinds of works"...

If you plan to make custom changes or new variants, be sure to read the Lullabot guide to new icon creation

This is a great set of icons, the free source (psd) files are available here

Enjoy!

In addition I've added more free icons from yellowpipe.com