🏛️ Open Library - Internet Archive's online library and catalogue of every book ever
https://openlibrary.org
📚 Inventaire - Free open book lending site and catalogue
@inventaire
🔎 Public Domain eBook Search - PD eBooks from many sites in many languages
https://switching.social/public-domain-ebooks-search/
🗣️ Librivox - Free public domain audiobooks read by volunteers
https://archive.org/details/librivoxaudio
📱 Libreture - eBook storage site and DRM-free bookshop list
@libreture