Zaidan Houjin Nippon Kanji Nouryoku Kentai Kyoukai Kyouryoku: Kanken DS Training

This game was suggested to me by a friend, and it's really magnificent! It has multiple sections with different approaches to kanji: not only how to read and write, but also stroke order and different readings in sentences.
It has level 10 through 1 on it, and thus anyone can start practising at their own level and gradually work their way up!