The http://www.kanjigames.com has free online versions of two mobile apps, 'Kanji Connect' and 'Lex Flashcard Game for Quizlet'.
Kanji Connect is a game like Boggle but the target word is cued with kanji or hiragana and meaning, and you need to spell out the word in the grid. Great thinking game to get to know kanji readings and meanings and learn new vocabulary - it also tracks progress and has reference flashcards.
Try the 'Lex Flashcard Game for Quizlet' app to use quizlet sets in a fun boggle/mahjong/crossword-style game. No other apps feature this kind of game plus pedagogical tracking/review.
Both games are also iphone apps available on the app store.
Soon coming is also the KanjiMatch3 app, great new game for focused learning of radicals and onyomi!
Enjoy!
Oliver