It’s inspiring how one person can collect and build such a great body of work at Guide to Japanese. Strangely enough, I found this blog when I was looking for a specific construction on Chinese.
Wikis are immensely useful for collecting and organizing information on languages. The Korean Wiki Project is a great example. I looked for an equivalent for Chinese but haven’t found one yet.
Professor O’s Learn Korean Videos are not only informative but also entertaining. I like the way she uses graphics and different characters to give examples of language use.