Alex @ Net

For you site or application or presentation or something else (order by Alexa rating):

• IconFinder - 164K of icons, 551 sets. Browse by set, tag, author. Converter, API. Custom icons service. Alexa rank: 3,508.
• Iconspedia - browse by category, set. Alexa rank: 5,663.
• FindIcons - 291K of icons, 2170 sets. Browse by set, tag. Converter, API. Alexa rank: 7,374.
• FreeIconsWeb - 20K of icons for operating systems. Alexa rank: 11,618.
• FreeIconsDownload - icons for operating systems. Browse by set, category. Alexa rank: 14,646.
• IconShock - 913K of icons, 248 sets. Browse by tag, set. Custom design service. Alexa rank: 16,097.
• VeryIcon - over 20K icons, more than 1000 sets. Browse by category. Alexa rank: 23,994.
• IconSeeker - browse by tag. Alexa rank: 44,638.
• IconLook - browse by tag. Alexa rank: 52,052
• Iconlet - thousands of icons. Browse by format, license, size. Alexa rank: 55,359.
• WeLoveIcons - 473 sets. Alexa rank: 94,840
• IconsSearch - Alexa rank: 123,516

Some good sets:

• Fugue icons from Yusuke Kamiyamane.
• Tango Desktop Project, Gnome and KDE desktop icon set.