Apprentice Alf's DeDRM Tools - Everything you ever wanted to know about DRM and ebooks, but were afraid to ask.
TunesKit iBook Copy for Mac - Easily remove DRM protection from Apple iBooks and copy DRM protected iBooks to DRM free ePub files.
DRMBuster - DRMBuster is a powerful all-in-one audio and video conversion software for any kind of purchased or legally obtained music and video.
AudKit AAX Converter - Full-featured AudKit Audible AAX converter to download and convert Audible audiobooks to MP3, AAC, M4A, M4B, etc. losslessly.
Sidify Music Converter - Sidify Music Converter for Spotify is a popular tool used to convert Spotify music to MP3/AAC/WAV/FLAC/AIFF/ALAC. It keeps original audio quality and ID3 tags after conversion.
OpenAudible - OpenAudible Project Page