Anki is an open source flashcard program for spaced repetition that hands the timing of reviews to the FSRS scheduler built into it, and includes a free service for syncing between devices. It suits learners who need to hold a large mass of small facts over the long run.

An open source tool for collecting, organising, annotating, citing and sharing research material. It reads citation data off a web page in one click, inserts citations while you write and rebuilds the bibliography, and keeps PDF annotations tied to the item. Version 10.0.6, AGPL.

Learners collect dictionaries the way other people collect records, and then look words up one book at a time. GoldenDict-ng loads the whole shelf and shows every answer for a single query on one screen.

A few hundred ebooks scattered across a download folder, with mismatched names and formats, is where management stops being optional. Calibre reads metadata on import, fills in covers and series, and converts between formats almost freely.

An open source reading application that puts its own interface onto several popular e-ink readers and onto Android and Linux. Reflow of scanned PDFs, dictionary lookup, export of annotations and progress that follows the reader between devices are all present, under the AGPL with the source open.

An open source reader for six platforms that opens more than fifteen ebook and comic formats, keeps everything local by default, and adds cloud sync, four annotation styles, translation and read-aloud for people who want to read rather than manage a library.