I stumbled across this site a little while ago:
http://game-icons.net
Really nice clean icons, good variety. There's still some gaps in categories so hopefully they grow over time. I'm loving the fact you can download the entire site in a zip file <img src="smileys/smiley1.gif" border="0" align="middle">
Hope you guys/gals find it useful.
(Note: I'm not affiliated with this site in any way)