http://hua.umf.maine.edu/Chinese/welcome.html

Unfortunately no longer online – instead I’d recommend using the Pleco app instead

The best site I’ve come across for learning Chinese – you’ll need to tweak your browser settings to get it to work properly though – make sure that it is set to handle simplified Chinese.

Features:
Dictionary search,
Flashcards / Review list,
A wide variety of sound files so you can hear words and phrases,
Flash – Talking maps, family trees, colours charts,
Account creation & storage so you can practice what you have learnt.

很好