I first used this dictionary during my first semester of Chinese and I have kept using it ever since. It has pretty good information about character etymology and provides more accurate information... Read more.

zhongwen.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

Outlier Linguistics hosts an excellent blog with a large number of insightful articles into Chinese characters. Some of them are directly useful because they talk about learning characters, others ... Read more.

outlier-linguistics.com

Outlier Linguistics Dictionary of Chinese characters is an excellent tool to help you understand and thereby learn Chinese characters more effectively. It gives you instant access to the latest res... Read more.

outlier-linguistics.com

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

Basic HSK grammar from beginner to advanced level. The best part is that in each lesson end, there is a quiz to test if you have really mastered the grammar. Read more.

hskcourse.com

Mastering Chinese characters, whether you find them enchantingly beautiful or overwhelmingly complex, is essential for literacy in Chinese. Outlier Linguistics will help you understand how the Chin... Read more.

outlier-linguistics.com

Character frequencies for Classical Chinese (i.e. not based on texts). This resource was discussed in this article: [The most common Chinese words, characters and components for language learner... Read more.

lingua.mtsu.edu

This blog provides in-depth explanations of some grammar and vocabulary topics in Mandarin Chinese. While there aren't a huge number of articles so far, there are enough to issue a general recommen... Read more.

mandarinfriend.wordpress.com