Macsome Audiobook Converter - Convert Audible Audiobook to MP3 / AAC at up to 300x faster speed and id3 tags kept.
OpenAudible - OpenAudible Project Page
TunesKit AudioBook Converter - Best audiobook DRM removal solution for Windows to remove DRM from iTunes and Audible audiobooks.
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.
Voice - Convert texts to audio files easily... Write your text, click export.
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.