[Re-post from lifehacker.com]
The FSI Language Courses web site isn’t actually maintained by the U.S. government itself, but the materials developed before 1989 are within the public domain (whether all of these materials came before then is not clear). Some languages contain more materials—for instance, the three texts on Sinhala isn’t going to beat the giant course on French anytime soon. For the most part, most major languages have student texts in PDF format, and audio in MP3 format which you can later put onto your music player. The courses also feature tests to see how well you’ve covered the material. In some cases, “headstart” courses for certain regions in the world are also available.
The only major language not covered is English, which makes sense. The site is a little reminiscent of old-school language learning, but the resources are ridiculously extensive. As a native Vietnamese speaker, I didn’t find the section archaic at all. Adios, Rosetta Stone.