Just in case you didn't find it already, I have a great Japanese/English Dictionary for my DS^_^ It's the Genius one and the cover looks like this:
http://www.nintendo.co.jp/ds/arjj/index.html
You can draw in kanji or type in hiragana and such. The only thing is, this is *meant* for Japanese people, so there is quite a bit of kanji in the definitions (although there is usually enough English to get the idea). I found it a little difficult to use at first, since I'm not great at kanji, but it really is a great one^_^