I just noticed today a new feature on the website of the Ministry of Environmental Protection: datacenter.mep.gov.cn.
My browser is giving me some errors loading the pages, so it seems they are still doing some debugging, but so far it seems interesting. The pie chart above displays fraction of Chinese cities meeting different air quality levels today.
There are also links to city specific sites (e.g. Beijing) that automatically display a graph of the last 30 days of API data for each city:
(Note the 10/18 pollution spike I mentioned in my last post).
Historical API data is also now hosted on the new site, here: http://datacenter.mep.gov.cn/TestRunQian/air_dairy.jsp. (The use of the term "test run" in the URL leads me to believe this is temporary, but we'll see; in any case the old API site has not yet been updated today so this is the only source of current data for now.)