Though its graph is a little bit old, but it's useful for your understanding a overview what services provided from each China's internet giants.
This graph have 18 category of main social service, and targets 10 internet company in China as following.
* Tencent (腾讯)
* Sina (新浪)
* Baidu (百度)
* Wangyi (网易)
* Sohu (搜狐)
* CIAC (千橡互动)
* Alibaba (阿里巴巴)
* SNDA (盛大网络)
Actually there is a little bit old data such as Baidu stop their Weibo service "Baidu说吧", but I think it's meaningful to understand the big picture of Chinese internet/social industry :-)
Original article => CIC on Sina-Weibo