Audible, long a supplier of my audiobooks, has released an app just for better managing of those audio files.
Since the introduction of the iPhone, you have been able to download audiobooks purchased through Audible and play them like any other audio file. All of the usual controls are there for jumping to the beginning/end, play/pause and view your progress.
The free Audible iPhone app takes your audiobooks out of iTunes and allows you to manage them in their own app. You can still have your files where they were, but the Audible app would really like you to download and play within their app. By doing this, you end up with more information about and finer tuning of your library. The app allows you to download, play and remove the files quickly (over 20 meg audiobooks do require a WiFi connection) so you only have on your device what you need without having to do a USB sync back to your iTunes based computer. The app actually encourages you to remove any audiobooks from the iPhone’s iTunes and run them only through the Audible app.
There are some extra features like Sleep Timer which will make it nice to not worrying about dozing off and waking to hear the end of the Who Did It novel. Surprising though, there is not way to search and buy new audiobooks, this only works with your current library.