I've used both Gutenberg and Librivox and both are great. I have found that some Librivox recordings are better than others. Lots of them have a different reader for each chapter of the book, since it is all volunteer based. However, look around some, many books have multiple versions and often you can find a version that has the same reader for all chapters. This is my preference because I listen to them at night to help me fall asleep. It's really jarring when you go from a reader with a soothing voice to a louder, more abrasive voice on the next chapter! Not all reading voices are equally appealing! But it's free, so I can't complain. Also, it's probably not an issue if you are awake when listening. :)
I really like the reader Karen Savage - she has recordings for several Jane Austen books and reads in a British accent. I like her versions of Pride & Prejudice, Sense & Sensibility, Mansfield Park, and she's also done a version of the Secret Garden and many others.
