Anki is a powerful, open-source flashcard program renowned for its effective spaced repetition system (SRS). It isn't a language course itself, but a highly effective tool for memorizing vocabulary, phrases, or grammar rules that you input yourself or download from shared user-created decks. Its high degree of customization allows for rich cards with audio, images, and cloze deletions. While its interface can be unintuitive for new users, its effectiveness for long-term retention is largely considered unparalleled for dedicated learners.

Mango Languages offers a structured, conversation-focused curriculum available for a wide range of languages. Its methodology involves breaking down sentences into component parts and encouraging the learner to construct them piece by piece. Lessons emphasize practical communication and are enriched with cultural notes. A notable feature is the voice comparison tool, which allows users to record themselves and visually compare their pronunciation waveform to that of a native speaker. Many users can access Mango Languages for free through participating public libraries, making it a very accessible option.