SSFAudio: reviews of science fiction/fantasy audiobooks ... what's said about the audio version applies to the print edition as well ... plus links to numerous related goodies.
The Spoken Alexandria Project: this site's goal is to be the audio version of Project Gutenberg, making public domain material available in a spoken form. It's in the early stages, so there's not a lot of free stuff available yet, but if you visit sister-site ...
Telltale Weekly, you'll find a wealth of public domain e-audio at twenty-five cents per download. Bargain pricing, IMHO. It appears that the plan is to eventually make this material free as well, but right now they're at the funding stage ... have a peek at their "mission/about" link to find out how they intend to make it all work.