low cost marketing

Independent publishing is going to be the wave of the future. Authors are going to need to learn marketing strategies like a Predictive Dialer or mass email campaign. As high speed becomes available in more places through Internet Satellite, DSL, and cable, people will be more apt to download books (audio and digital). The key will be to learn how to peak interest.
What simple, low cost strategies would you guys recommend for independent authors? What have proved to be effective. Any tips or advice welcome.