calibre - Ebook manager, viewer & converter
OpenAudible - OpenAudible Project Page
Convertio - File Conversion in the Cloud
DRmare Audio Converter - DRmare Audio Converter for Windows is a complete audio DRM removal tool designed to convert both protected audios, including Apple Music, Audible audiobooks, iTunes music, and common audios to MP3, WAC, FLAC, M4A, AAC, etc.
CBconvert - A comic book converter with support for .cb*, .pdf, .xps, .epub, .mobi and directories.
TunesKit Audible AA/AAX - Audible AA/AAX Converter by TunesKit is an application that enables you to convert audible AA and AAX files to the formats that are supported by other devices.