You might already know magnatune, but the discovering it today really made my day.
"Founded by musicians, for musicians", the label is selling online using a "try before you buy" approach they call "the shareware model applied to music".
I guess my first purchase will be Vito Paternoster's recording of the Bach cello suites, an long-time favourite of mine. I'm amazed each time I hear a new interpretation.

Apropos downloading music: Everybody is downloading the Grey Album right now.. even though it's not that amazing at all, IMHO. But great marketing for a next album, of course.