LibriVox - free public domain audiobooks
Rocketgraph - Rocketgraph is an open-source drop in replacement to Firebase, except it's much better.
Audible - Audible is the world’s largest provider of premium audiobooks and spoken word content.
Plug - Lightweight OSX player for Hype Machine
Mobilism.org - A home for book lovers, app enthusiasts, and much more.
Muru Music - Personalised playlists within seconds.