CIA World FactBook
http://www.cia.gov/cia/publications/factbook
Basic economic, governmental, and demographic data for nearly every country in the world.

China-Britain Business Council
http://www.cbbc.org/china_guide
Website offers detailed and useful information for understanding basic Chinese business practices

The Embassy of the PRC in the United States
http://www.china-embassy.org/eng

U.S. State Department Information on China
http://travel.state.gov/travel/cis_pa_tw/cis/cis_1089.html
As the name suggests, this site offers helpful information on China