One of my all-time favorite icons sets is Buuf by mattahan. They have an amazing quirky style that looks almost like they're molded out of clay, and the names for the files are hilarious. Back in 2006 a few of our skinners contacted mattahan asking if they could convert his icons to Windows (he's a Mac user). He consented and we got the great Buuf icon set from rgerrans.
Well, turns out mattahan is at it again with a second Buuf set, and our friends at Shellscape have converted it for use with IconPackager, and provided a download with the original images in 128x128 png format.
The download is 100% free. You can snag it here.