Free Audiobooks/podcasts are a bit on the side when it comes to ebook readers, but I'm sharing it anyway.
It's written by Mercedes Lackey and Steve Libbey, and is a scifi serie.
http://www.secretworldchronicle.com/
I have heard the first book, and I like it.
There is also one free ebook or audiobook available by Steve Libbey named "The Bloodbaths":
http://www.aquapuratrilogy.com/