Yes visa is required. You will need to either go to a Chinese consulate in person or use a visa service. I have used www.mychinesevisa.com and they were very quick and efficient.

You can use the form at the bottom of this page to check visa requirements. Simply fill in your destination country or countries.
http://www.delta.com/planning_reserv...tion/index.jsp


While true in most practices, passengers with US and other passports arriving in Shanghai via air can visit the city for 48 hours without a visa.
http://www.china-embassy.org/eng/hzqz/zgqz/t84242.htm