If you feel like spending some cash on a specific language, I recommend rosettastone. I got a hold of it through a friend awhile back and it seems to be pretty accurate, i.e. I ran through the English lessons and everything checked out, as well as the Russian lessons. I couldn't tell you how any other languages check out, as those are the only 2 I know fluently (English first, Russian second). All in all though, if you really want to learn a new language, it's worth a definite look.
http://www.rosettastone.com/