Jappy is a Japanese dictionary program I wrote for myself. I have a whole laundry list of features I mean to implement but probably never well, but it's already pretty useful. It has word lookup, text translation help, example sentence search, and study helpers. Plus, you can easily jump between different parts of the program -- highlight some text and right-click to search on it. Or click to translate Japanese example sentences. Or click a headword to see example sentences containing it, etc. It's somewhat outdated now.