I'm glad this thread resurfaced, and I've got one to add I haven't found here.

Zhongwen.com - Chinese Characters and Culture
http://zhongwen.com/

You don't even need language plug-ins for your browser! It's all graphics for the chinese characters, with very extensive links. English to Chinese dictionary. Pinyin imput to see characters, with back to english translations. Grammar and other useful things. I came across it when I needed help verifying some characters I came across with poor translation. Didn't want to look a fool using chinese in art, and have it say something stupid.

Ali