That's a great site! The one I use most is here:

http://simplemedia.org/kana/

This one gives you ten seconds to type the answer, so, the time factor has helped me get better and more automatic in my recognition.

And I'm currently learning Japanese off this site:

http://www.guidetojapanese.org/completeguide.html

It makes you learn grammar in a "think like a Japanese-speaking person thinks" way, and gives you the vocab and kanji to accompany every new lesson. I really like it!