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

Recommended and introduced by Trevor [here](http://www.hackingchinese.com/extensive-listening-challenge-october-2014-wrapping-up/#comment-646686). Each book (one for each level of the new HSK ex... Read more.

amazon.com

A website on the etymology of Chinese characters, with a lot of images of their past forms from different periods. Read more.

chineseetymology.org

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

Ideally, we would study Chinese just because we want to and in any manner we see fit, but this isn't how it works for most students. Instead, we need to care about tests and grades, an extra layer ... Read more.

hackingchinese.com

This website offers a large number of previous HSK and YCT Chinese proficiency tests, sorted by year and level. This is excellent for test preparation and/or benchmarking. Read more.

chinesetest.cn

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