Just thought I'd drop this here. Found it while looking into a game contest I am considering entering.
My plan is to redo my SampleGUI (because I don't know where I got the art, and my Photoshop hack job is hideous) with these graphics, because I know they are legal for use. Most of them are Creative Commons licensed.
Check it out if you want to do some GUI work.
GUI Assets
Re: GUI Assets
Seems interesting, though won't be making use of this stuff for a while, but nice to at least check it out now.