I have an Audible.com subscription as well as for a few book summary sites, but I like the concept of a blogcast - a "Readers Digest" audio version of books, blogs, and general topics. These are fun to listen to, especially when you don't have 45 minutes to listen to a book summary or regular podcast. Blogcasts range from 5 to 15 minutes in length, and hit the main points of the blog, book, or topic. A great way to know the basics about something!