Selling your music digitally... what are the options?

[Gabba Flamenco Crossover]

I've been getting a good reaction to my tracks on myspace, so I wanted to investigate options for selling mp3s online. Beatport aren't taking on any new labels, so I was looking at Bleep and Boomkat. Does anyone have any experience of getting onto these services with microlabels, how easy/hard is it?

Failing that, are there any more services out there that provide the back end for selling downloads of your own music on line?