Free public-domain US government language courses with textbooks and audio.
CoursesBooks Free BeginnerIntermediateAdvanced A1–C1
grammarlisteningspeakingreading
Details
Foreign Service Institute, Peace Corps and DLI materials — full textbooks plus hundreds of hours of audio — are public domain and hosted here for free across dozens of languages. The depth is extraordinary and the FSI Basic courses take diplomats to professional working proficiency, which no consumer app attempts. The recordings are from the 1960s–80s, the drills are relentless, and some vocabulary is dated (Cold War era), so they suit disciplined self-studiers, not casual learners.
Century-old bilingual course books that take you from zero to solid B2.
BooksCourses Paid BeginnerIntermediate A1–B2
readinglisteninggrammarvocabulary
Details
Each course is ~100 short bilingual dialogues with native audio: you passively absorb for months, then start an 'active wave' translating back into the target language. Books run around €30 (e-courses ~€50) across 70+ languages, and the method is a long-standing favourite among polyglots for reaching real reading fluency. Caveats: many courses are only published from French, the humour is dated, and it demands daily discipline with no gamification to carry you.
Routledge's beginner course books with free downloadable native-speaker audio.
BooksCourses Paid BeginnerIntermediate A1–B1
readinggrammarvocabularylistening
Details
Over 70 languages, each a step-by-step beginner course written by an experienced teacher, and crucially all the audio is free to download from the companion site even if you find the book secondhand. Slightly more academic and grammar-forward than Teach Yourself, which some learners prefer. Like any book series the individual titles differ in quality; the less common languages are often the only decent course in existence.
The reference grammar English-speaking Danish learners actually keep on the desk.
Books Paid IntermediateAdvanced A2–C1
grammarwriting
Details
Robin Allan, Philip Holmes and Tom Lundskær-Nielsen cover Danish morphology and syntax systematically with English explanations and plentiful examples, indexed so you can look up a problem rather than read it front to back. Danish is thin on serious reference grammars in English; this is the standard one. It is a reference, not a course — there are no exercises and no audio.
Self-study course books with audio for 30+ languages, beginner to advanced.
BooksCourses Paid BeginnerIntermediate A1–B2
readinggrammarvocabularylistening
Details
The 'Complete' books are proper structured courses with dialogues, graded exercises and downloadable audio, and the range covers languages no app touches. Quality varies noticeably by title and author, so check reviews for your specific language before buying rather than trusting the series name. Their graded readers and 'Script Hacking' alphabet guides are also worth knowing about for non-Latin scripts.