First of all, as I think, Last.fm should be top-1 site you should consider in both situations, because this is a music-based social network!
The second one is Bandcamp, that was already mentioned. It provides you an ability to be enough flexible in in the means of royalties for your work.
Further answer depends just on the one thing. Do you you have desire to share music for free or to ask money for it?
If you are not going to sell your music, try to put it on torrent trackers, as well as on closed invite-only music trackers like Waffles.fm, What.Cd, JPopsuki.eu(asian music) and others. Obviously you need an invitation, but you can get one for What.Cd easily by passing an interview.
Also, I would suggest finding communities connected with such music, like forums or discussion boards.
If you want to sell your music, try audio stocks. Personally, I can recommend Audio Jungle, Pond5, Revostock and iStockPhoto(don't look at the site name, it has audio section too).
Unfortanutely, I can't add links to all these sites because I have no enough reputation, but you can just google them :)