Audible for Android is here!
Audible has created a fantastic Android app. No computer or other software required, just download and do everything right from your phone.
There are many options such as only download on wifi, set audio quality (standard or high quality), and others. Audible really did an awesome job with this app.
Here are some pics:
Android users, scan to install Audible:
For more, see http://www.audible.com/wireless/android