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 probably one of the best resources for upper-intermediate or advanced learners of Chinese who want to learn something using their Chinese. Khan Academy has hundreds of videos about differen... Read more.

youtube.com

HiNative is a Q&A site where you can ask people all over the world about culture, language, anything. We support over 100 languages. Read more.

hinative.com

This is a research paper detailing a study of the mutual intelligibility of Chinese topolects. Dialects were sorted into groups and then it was experimentally tested how much of words and sentences... Read more.

openaccess.leidenuniv.nl

This is a review of Perry Link's book about Chinese. This passage sums it up pretty well, and although I haven't read the book (yet), it's high on my list of books to get my hands on: "In writin... Read more.

lareviewofbooks.org