If you're into classical music, and Beethoven in particular, you'll want to check this out:
BBC: The Beethoven Experience
Such a deal: All of Beethoven's nine symphonies, free for downloading. It's a limited-time thing, so you'll need to pay attention to dates. Navigate that obstacle, though, and you'll have free (good) music.
And whilst I'm thinking about it, a very good place to peruse classical music CDs is Naxos.com. Naxos' claim to fame? Quality classical recordings at really nice prices — usually $9 or so if you buy them via Amazon. Plus you can get absolutely lost (in a good way) in their website.
The Naxos CDs in my library are all high-quality recordings, and very much worth the money.
And if you have a half-day to kill, Naxos' "Classical Music Experience" (free w/registration) offers an extensive online classical-music tutorial, complete with audio segments.
If you're really cheap, ClassiCat is a directory of free classical recordings available for download on the 'net. Why, just tonight I tracked down some pretty good Mozart MP3s through there . . ..