Amazon platform ACX can turn your book, if you're a published author, into an audio book. It means your audio book can be distributed through Amazon, iTunes and Audible. It's really easy to sign up and use but at present you need to be resident in the US. It's a great way of getting your written word out to a wider audience using audio. Considering that only around 5% of the world's books are in audio form there's still plenty of opportunity!

Audiobook Creation Exchange (ACX): http://www.acx.com
Get your book transformed into an audio book at: http://www.musicradiocreative.com