This is a course offered by Peking University and Coursera. It's free to use, but you need to register (you can preview it before you register, though). There are six units, each taking roughly one... Read more.

coursera.org

This website and podcast offer theme-based, progressive online audio lessons. There are transcripts, worksheets, mobile apps, videos and more. Not all of this content is free, but the beginning of ... Read more.

melnyks.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 newly launched site offers basic information about pronunciation, mostly things that should be in all beginner courses and textbooks but seldom are. Currently, the content is fairly limited, b... Read more.

resources.allsetlearning.com

Duanmu San's "The Phonology of Standard Chinese" is by far the best introduction to Mandarin phonology that I'm aware of. It's mostly useful for people who like phonology or are already at an advan... Read more.

hackingchinese.com

This website allows you to look up all sorts of things related to characters, including pronunciation in historical and regional varieties, components based on their pictographic origin, and much m... Read more.

zi.tools

This is a digital version of the official authoritative stroke order standard used in China. It is sorted by stroke and is not searchable, so it's a bit hard to use. Thus, other resources will ofte... Read more.

yuke.blcu.edu.cn

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

ChineseMe is the most integrated Mandarin course, designed for motivated learners who have decided to become fluent. It is an interactive textbook that adapts itself to your interests. The course i... Read more.

chinese-me.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

This is a character-by-character beginner course in Chinese, provided free of charge at the Open Languages Project. It teaches you to read (and listen to) Chinese by explaining and introducing one ... Read more.

oplang.org

This site offers basics, self-paced lessons where you can learn basic vocabulary and grammar (usually with audio as well). There are also Skype lessons and other more interactive parts of the site ... Read more.

culturealley.com

Have you ever wondered how names from other languages are transliterated into Chinese? There is actually a reference table where you can see how different sounds are translated into Chinese charact... Read more.

en.wikipedia.org

What's a dialect? What's a language? Are Mandarin, Cantonese and Wu different languages or are they dialects of the same language. The answer is that there is no answer, it depends. This is a short... Read more.

sinoglot.com