Church Planting efforts by Christian Missionaries in the Chinese Municipality of Chongqing is probably one of a large number of uses of the Web to publicize present activities, but it's hard to gauge just how useful such things can be... likewise, sites like UNREACHED PEOPLES PRAYER PROFILES seem to offer a lot of detail, but it's hard to see how they illumnate your topic.
CHINA: Seeing Beyond the Impossible is another that's hard to fit in to anything analytical.
I did a google.com search for "christian missions in china" (with the quotation marks) and got a number of what looked like useful sites, though many of them are historical rather than the contemporary I think you're most interested in.
I have the impression that outside missionaries are active once more among the minzu in southwestern China...
A search for "house churches" might be productive. See China's House Churches for a good start on that.