The traditional way to self-publish music is still a viable one, assuming you play regular shows and have an outlet through which to sell your music. Designing a cover and paying a duplication firm to run off a number of copies is a good way to retain total control over how everything looks, sounds and is sold. It does however limit distribution to those geographical areas that you can physically reach.
iTunes is a hugely popular application, an article from "AppleInsider" in 2007 reported 500 million active users. Publishing your music on iTunes would make it immediately available to all of them. However, there are fees and costs to host music on iTunes, and there is no way for users to promote their music directly in the application. The only option is to try and create a separate online buzz, and direct users to buy the tracks on iTunes.
Amazon.com's user-created marketplace, "CreateSpace," allows users to upload material, and create Amazon.com pages for it, just as any other retailer would. As with iTunes, there are no integrated marketing tools, and it will be up to you to direct people to the ad. Createspace allows both digital downloads, and ships physical CDs. It has the advantage over traditional duplication of not requiring any setup costs. Amazon.com recoups its costs on each individual unit, rather than requiring an upfront lump sum from the publisher.
These two sites are musician communities that allow the uploading of tracks for streaming, but not downloading. Similar to the way in which YouTube functions, they are geared more toward marketing music than selling it. They also allow full integration with social networking sites such as Facebook, Twitter and MySpace, allowing users to post uploaded tracks on their profiles. People who wish to buy tracks are then linked to a retailer such as iTunes or Amazon.com, so a separate account for those sites will be required.