LibriVox - free public domain audiobooks
Smart AudioBook Player - Smart AudioBook Player app comes up with features to help you in casting all your audiobooks to Chromecast enabled devices so you can enjoy them with your friends and family members.
Audible - Audible is the world’s largest provider of premium audiobooks and spoken word content.
Voice - Convert texts to audio files easily... Write your text, click export.
Mobilism.org - A home for book lovers, app enthusiasts, and much more.
Libro.fm - A digital audiobook platform for independent bookstores