[korriken]

I've been messing with the Japanese Coach software for the DS myself, i find it is a good supplement to book learning. One good thing is that it does not allow you to skip ahead. ever. Also, the kana lessons on it is what taught me how to write Kana. It's a fair tool to practice Kana with, as well as drilling yourself on the words. The software also contains a decent sized dictionary. Also, every word comes with an audio pronounciation, which has helped my tremendously and is something you don't get with a book.

For those who can't afford the extremely expensive books, this isn't a standalone substitute, but it will get you started.