So I'm working on a website, and need icons for 'email this page' and 'print this page'. Where to go? I started with a google image search for 'open source icons'. This was a good start but pretty random and all over the map. Clicking on the first few links basically got me random blog entries of people looking for free open source icons, with some images of some stock icons. Nothing that really popped out at me right away.
Some sites that I stumbled across with icons available (some free, many not):
Designmagus.com, http://mouserunner.com/Spheres_ColoCons1_Free_Icons.html, http://www.iconbuffet.com/, http://www.ganato.com/free_icons/free_icons.php, http://dryicons.com/free-icons/
Wikimedia has a number of free open source icon sets available. This is probably the best place to find what you're looking for, though it took me a bit to figure out how to search for what I was looking for. I found two here that seem pretty straight-forward and good enough for me. For example here's the Crystal Clear icon set, which I may end up using. Or I may go with the GNOME desktop icons. We'll see...