Reading Kanji and Hiragana/Katakana online

I recently watched a videoclip by a guy called Gimmeaflakeman where he describe the use of, and link to, a very useful plugin for Firefox called Rikaichan. Along with a dictionary (also found on that site) you can hover Kanji or Hiragana/Katakana and it will translate the words in a popup. Either watch the video or go to their site for a preview. Really nifty plugin. :-]