The thousands of volunteer readers who bring over 100 new books a month originally in Project Gutenberg, and other public domain sources (including, of course, the Internet Archive) to the listening public.
With over 7,000 audio books, LibriVox is one of the largest publishers of audiobooks in the world, and certainly the largest publisher of free public domain audiobooks.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.