TunesKit iBook Copy for Mac - Easily remove DRM protection from Apple iBooks and copy DRM protected iBooks to DRM free ePub files.
Audiobook Builder - Audiobook Builder is a software that enables users to turn their audio files into audiobooks which they can sue then on their iPhone, iPad, or any other Apple devices.
AudKit AAX Converter - Full-featured AudKit Audible AAX converter to download and convert Audible audiobooks to MP3, AAC, M4A, M4B, etc. losslessly.
AudioBookBinder - Got a lot of audiobooks in MP3 format and would like to listen them on your iPod?
OpenAudible - OpenAudible Project Page
UkeySoft Audible Audiobook Converter - UkeySoft Audible Audiobook Converter is a popular AAX/AA to MP3 converter, it not only can remove DRM from Audible books, but also can convert Audible AA/AAX audiobooks to MP3, M4A, AAC or FLAC with 100% original quality preserved.