There's a site,
http://librivox.org/ , where they do something similar to what this forum does with public domain ebooks - volunteers read the books, and they publish audiobook versions. The skill of the readers is variable - some of the readers do a fantastic job, others not so much. And the books are sometimes done as a team effort, so the reader changes from chapter to chapter. Still it's a good source.
Audiobooks tend to be expensive, and the available choices are skewed towards potboilers, so it's nice to have other options.