Read this very good article how unsigned authors are utilizing podcasting and growing there readership/ listeners. Below is a quote from Mr Sigler who currently has 30,000 listeners

“A lot of no-name authors like me are getting massive grass-roots exposure, and some of us are going to percolate to the top and get on the best-seller list,”

You can find the book which comes in instalments over at Podiobooks. They suggest a donation of 10$ for new covers but frequently people pay over when they enjoy it