wikibooks
I was super excited to see this wikibooks entry, but unfortunately only two lessons seem to be built to a decent level. The lessons on pronunciation are also quite nice — except for the obvious lack of sound. For all the years I taught and learned Chinese, I never thought to teach the third tone as different before first and second tones, but it seems right. Take a look at the tones section to see what I’m talking about: http://en.wikibooks.org/wiki/Chinese.
I downloaded moodle the other week to see if I could figure out a way to offer an online Chinese class. I thought this might be the perfect text solution, but it’s not ready yet… and so I keep searching.

I've been teaching Chinese since 1998. This site was built to help my students practice the sounds of Chinese. Hope it continues to help others. Let me know if you have questions.