The US gov't foreign service institute (FSI) spent a great deal of time and money developing extensive language courses for their staff. Coursework includes workbooks, teacher's guides, study guides, and audio material.
It can be purchased in a very slightly modified, but nice package from Barron's and other places. However, almost all of it is available free public domain from various sources. The web page and forum here FSI Language Courses is the best place to start for help finding complete files to download and more information. They have languages I've never even heard of and and lots of links to more information on learning languages
The bad news is, that FSI courses actually teach well because YOU have to put a lot of work into it.
The Pimsleur language learning system is not free, but it also works well and is Ipod friendly. Since it is audio-based many libraries have it available. It is all audio, the listener constructs phrases or repeats from memory out loud along with a recording.