日本語

Dictionaries

Perapera-kun

Japanese popup translator Firefox add-on. When turned on, you can simply move the mouse over some kanjis to have the reading and meaning displayed in a pop-up. This is a killer app.
After installing the add-on, you also need to install dictionaries from here:
http://www.polarcloud.com/rikaichan/

SPACE ALC (アルク)

Japanese-English, English-Japanese online dictionary. Not great, but the best that we know, with many example sentences.

FOKS (Forgiving Online Kanji Search)

FOKS is a Japanese-to-English dictionary which allows lookup by reading, and can correct for many common types of reading errors.