http://www.bjgaj.gov.cn/(北京市出入境管理局)
Beijing Public Security Bureau
The authority that extends visa and will define policies to ensure public security.

http://www.bjld.gov.cn/ (北京劳动保障网)
Beijing Labor Bureau .

http://beijing.caiep.org/(北京市外国专家局)
Beijng Administration of Foreign Experts Affairs.

http://www.safea.gov.cn/（国家外专局）
State Administration of Foreign Experts Affairs .

http://www.beijing.gov.cn/ (首都之窗)
This is a very useful website, almost every information about Beijing.