This site by Jun Da contains a lot of very interesting resources for anyone who wants dig deeper into frequency lists. One set of data I haven't found anywhere else is a frequency list of syllables... Read more.

lingua.mtsu.edu

This is the best overview of spaced repetition research I have seen online or offline. It's thorough, well-argued and probably covers more than you were looking for. It's not specifically about Chi... Read more.

gwern.net

Word Reference offers several good forums for discussing languages and this is the Chinese section. It's perhaps not as active as Chinese Forums and I don't follow this forum regularly, so I don't... Read more.

forum.wordreference.com

Forumosa is a major online forum where you can discuss anything regarding Taiwan, including living there, learning Chinese, finding friends, jobs or language exchange partners and much more. There'... Read more.

forumosa.com