I've tried off and on to learn Japanese (for, basically, free), and found a good app last week that some of you wanderlust or cheap people like me would want:
basically: free version goes over hirigana, half of katakana, about ~50 vocab words, minor (and rather redundant) culture points, but no kanji. It has some simple multiple choice review questions, and a matching tile game (which wouldn't be my first choice for a game, but, eh...)
I tried learning on the Nintendo DS with their My Japanese Coach, which was better for learning how to write (because touchpad), but My Japanese coach had a sudden, dramatically sharp learning curve about 1/3 the way through that killed it for me. So far, this app has a gentle learning curve. While I wouldn't use it solo, it is great so far.
It has a paid version which I will probably get once next paycheck goes through.