Great Downloader easy to use can convert into multiple file formats. Fast and impressive
OpenAudible - OpenAudible Project Page
Video DownloadHelper - Browser extension to download videos from the Web
AudKit AAX Converter - Full-featured AudKit Audible AAX converter to download and convert Audible audiobooks to MP3, AAC, M4A, M4B, etc. losslessly.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
TunesKit iBook Copy for Mac - Easily remove DRM protection from Apple iBooks and copy DRM protected iBooks to DRM free ePub files.
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.