What is the most inexpensive way to listen to audio books while exercising?

My mom is interested in playing audio books from her phone although I guess I could get her set up with an IPOD to serve the same purpose. She really just wants to listen to books while exercising. Where do I find books online to IPODS or cell phones? What is the cheapest way to do this?|||Yeah the library is the cheapest way.|||You could go to the library and borrow some audio books and just down load them onto your ipod. That is free! The cds could be played on any system, so you could hold off on the ipod for your mom if you want. Most libraries have a large selection, just find a larger library. Have fun!