Sorry about the deluge of posts today. I've recently returned to China after some time away in the States and am playing catch up on everything I missed.
Here I'm posting two additional databases of Chinese APIs outside of MEP's datacenter. Neither database has new data outside of the government-issued API data, however.
First, the Clean Air Initiative for Asian Cities has excellent China air quality data sets available for downloading. For example, Beijing APIs from 2000 to mid-2008 (along with tons of analysis) available on this page. Note that data for other cities may be downloaded at the bottom of the page. Note also the excellent API to pollutant concentration converter on the right.
Second, in late December, Imagethief posted "all the data you ever wanted on Beijing and Shanghai air pollution." In the post, he links to a 5MB Excel file containing daily API data for Beijing and Shanghai from 2000 through mid-2007. The spreadsheet also contains a lot of analysis.
Some day I'll post my own spreadsheets, but that will require me to clean them up (a lot) and also figure out a way to share files easily. I'm sure there's a way, I just haven't looked into it yet.
In any case, as you cut through the data from the above sources on your own, let me know what you discover!