Here’s the description on their website:
LibriVox provides free audiobooks from the public domain. There are several options for listening. The first step is to get the mp3 or ogg files into your own computer.
LibriVox volunteers record chapters of books in the public domain and release the audio files back onto the net. Our goal is to make all public domain books available as free audio books.
Although most of our staff still enjoy reading more, there are times when you just want to listen to a story, told by a soothing voice. You know, like the good ol’ days.
In the case of our staff, we work with our book posters while listening to books being read!
We are such bookworms.
— Postertext team