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

Finally, Duolingo added a En->ZH course. As Duolingo is the most popular gamification learning app, the learning experience is relatively streamlined and tested. The monetarization aspect leads to ... Read more.

en.duolingo.com

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

This is a Q&A page where teachers answer questions about Mandarin, mainly vocabulary use and grammar, but sometimes other questions as well. It's mostly useful because of the wealth of information ... Read more.

hwjyw.com

A blog written and managed by an advanced Chinese featuring reviews of books, TV dramas and games. Additionally, the blog also features recommendations for utilising media in Chinese language learn... Read more.

thecozystudy.com

This is a very in-depth article about how Pinyin is written, focusing mainly on the letters used, the typeface, arrangement on the page, and so on. It probably contains more about this topic than y... Read more.

thetype.com

This is a free e-book with a collection of articles about how to learn Chinese, to which I have contributed one chapter about listening ability. This is a good collection overall with contributions... Read more.

livethelanguage.cn