I'd definitely recommend [app]Japanese[/app]. It has animations to teach you how to write hiragana, katakana, and a lot of the kanji. It has a dictionary (a little outdated at times though), the different forms of a verb (eat = taberu, don't eat = tabenai, can eat = taburareru, etc). The hyperlinks make finding kanji compounds easy to find, and easy to find out how to write and pronounce.
The [app]Wisdom[/app] English-Japanese dictionary requires you know your hiragana and katakana well, but it really is the most up to date and non-native Japanese speaker friendly dictionary.
[app]Pocket Japanese[/app] will teach you basic Japanese vocabulary, grammar, and usage. It's not bad.
I haven't tried [app]Japanese Phrases & Idioms[/app], but it gets excellent reviews.