WindowMaker -- Icons by the Windowmaker project
DigitalGarage -- Carbon fibre and chrome...
KDE3 -- Independant KDE icons
KDE1 -- List of icon sets from the KDE site
XPenguin -- Fantastic icons for websites
KDE2 -- More KDE icons
Vinny -- Nice colourful icons (AOL page)
DeviantArt -- DeviantArt's galleries of icons
While many of these icon sets come from the various linux projects, icons are standard things which should work equally well in any application. See the Graphics programs section for software if you need to convert any icons, and the Compression programs section for reading any of the compressed files
