I think it was last Friday that I linked to some free music from The Strokes; that link was from ExploreMusic.com, which is a fairly excellent music blog that talks about nearly everything music-related. It’s run by Allan Cross, who also does an ExploreMusic radio show and also A History of New Music (I think that’s what it’s called – I don’t usually listen on weekends unfortunately).
So it makes sense then that ExploreMusic is also a pretty great source for free music. Here’s the link – they have new free tracks every Friday. Most of them are likely available indefinitely, but there are some (like last Friday) that are time-limited