The Joint Language University (JLU) provides free downloadable language courses. I have stumbled upon them while searching for the Portuguese learning resources, and I was pleased to discover more languages.
The JLU Free Language Courses
If you point your browser to the JLU’s address you will open a page with the following language courses: Albanian, Belarusan, Bulgarian, Cantonese, Chinese Mandarin, Czech, Dari, Dutch, Egyptian Arabic, Filipino, French, German, Greek, Haitian Creole, Hungarian, Indonesian, Iraqi Arabic, Korean, Maranao, MSA, Persian, Polish, Portuguese, Romanian, Russian, Serbian, Spanish, Syrian Arabic, Tausug, Thai, and Vietnamese.
The courses vary in quality and extent. For example, the Portuguese course contains several books and audio resources, while the Serbian is much smaller and lacks audio. The Russian resources are extensive. The Arabic courses are impressive, with Egyptian, Iraqi, Syrian and MSA. But, there is a catch.
Free courses, but dated language courses
The good thing about the JLU free resources is that they are, well, free. Not so good about them is that they are very dated and, form the point of view of a general learner or speaker, overly military (due to its origin and purpose).
Some of the materials are from 1960s. For example, the Portuguese course was created in 1968 (the PDF is scanned mechanically typewritten content, and the MP3 is converted from tapes). The Portuguese language underwent several orthographic reforms in the meantime, which the JLU course renders more of a research material than a learning material.
I assume that “dated” is a relative term for some languages, but it is up to a learner (or mentor) to give the final judgement. However, a half of a century is a lot in terms of a current and relevant learning material. The methods in language teaching have also been updated since 60s.
The JLU language courses listed in this text are not modern, but they can be useful to linguists and language enthusiasts (even though some courses are incomplete). You can have a look at their other public materials here, but be ready for not so friendly web interface.