The FSI language courses are excellent language courses made by the US government. The courses are very in-depth and thorough, and contain both textbooks and audio. They are fairly expensive to buy from the government, but since they are produced by the US government using tax dollars, they are in the public domain. Here’s a site I found recently that is slowly putting a bunch of them online (pdf texts plus mp3 audio) for free download:
http://fsi-language-courses.com/
The Foreign Services Institute obviously does not make courses for ancient languages, but we have enough polyglots here that some of you will probably be interest. So far, they have some or all of the following (with more promised):
Chinese (both Mandarin and Cantonese); French; German; Greek (Modern, alas); Portuguese; Serbo-Croatian; Turkish
As a side note, there are some companies that sell modified versions of FSI courses (Barron’s is one that comes to mind). Of course, it is perfectly legal to resell the material since it is in the public domain, but these companies also modify the courses and these derivative works are not in the public domain and cannot be shared. The website above accepts only public domain material.
) modern Greek in case anyone is interested in looking it up: It’s not as if it’s not almost up to date but not really.