You could sell some songs (or, extended versions of songs, give some away free as a hook, then sell the extended version/full album.

Here is some software to sell downloads:

PayVeX:

Just selling songs can be kind of difficult, if no one knows your music, they might not be inclined to purchase it.

One thing you can do for free downloads is collect contact information and then ask them questions, (did you like it?)

There are online services allowing you to do the same thing, but, these places charge a commission.

DownLead:

This will help for that, at a risk of driving away some would-be free downloaders.

Where downlead could really be helpful is podcast users. You, as a musician, could customize music for podcasts.

The idea, allow them to download a free song, using downlead, then, contact them asking if they liked it, what were they looking for? and finally, offering to customize a song for them. Sort of the “audio version” of web design

Some people are having success in this area, not just podcasts but also commercials (and indeed, commercials /in/ podcasts)