Do you read well aloud? Do you know how to record your own MP3s? If so, you should think about volunteering with LibraVox:

LibriVox volunteers record chapters of books in the public domain, and then we release the audio files back onto the net (podcast and catalog). Our objective is to make all books in the public domain available, for free, in audio format on the internet. We are a totally volunteer, open source, free content, public domain project.

I wanted to volunteer for a chapter of Three Men in a Boat, but they are all claimed!