WooFunction is a set of 178 beautiful icons that are created by Liam McKay for WooThemes.
Icons are available in 32*32px (some are 16*16px) & in transparent PNG format.
This set is awesome, plus if you are building a web application there is enough in there for you to use for most tasks. One of my pet-peeves with free icons is that there might not be that one icon you REALLY need - no issues with that here!
The set is very suitable to be used in web applications as it has all the vital icons like actions, arrows, documents, users & more
Link: http://www.woothemes.com/2009/09/woofunction/
Interesting, I`ll quote it on my site later.