I contributed to another thread on a similar topic and I figured, what the heck, I'd go ahead and point out a couple of my favorite music sources.
They say there are four doors to hell for an artist: government sponsorship, corporate sponsorship, crass commercialism, and obscurity.
File-sharing programs have opened a new door for artists who are unable or unwilling to inject their music into the mainstream through traditional major-label avenues.
I hate top-40 and I listen mostly to live music recordings. Many artists give their live product away and there are websites deducated to trading/sharing that product.
bt.etree is an archive of live music from "taper-friendly" bands that's available for download through the BitTorrent system. BitTorrent is extremely easy to use and there's a link to a FAQ and a download source at the top of the page.
The Internet Archive has a bunch of free content, including ebooks, spoken word, and music. The above is the music link. Have fun exploring; about 98% of these bands were new to me when I found this site.
It's nice that I'm not forking over eighteen bucks a CD for this stuff, and the best part is that it's good music.