Though this graph is a little bit old, it's useful for your understanding. It's an overview of what services are provided by each of 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)
* 360
* Kaixin(开心网)

Actually, there is a little bit of old data, such as Baidu stopped 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