Oh my 神様！ I cannot praise this site enough!
As a student of the Japanese language, this site beats all other dictionary-type reference resources by far and away. Blows everything else out of the water. I don't even go to other sites anymore when looking up Japanese info.
Want to search a gigantic body of words?
Want to look up Kanji by radical? And research the meaning of the component radicals?
Want to search the sentence database for phraseology, methods of expression, content-specific terms, etc.?
And stroke orders? And external references? And multiple dictionaries? And Kanji metadata? And various search criteria?
etc., etc., etc.