Chicago Board of Trade (CBOT)
The CBOT is best known for trading grains.
Active markets traded: corn, soybeans, soybean oil, soybean meal wheat, oats, ethanol, rough rice, treasury bonds, treasury notes, Dow Jones futures
Chicago Mercantile Exchange (CME)
The CME is best known for the S&P 500 and the ag markets.
Active markets traded: live cattle, feeder cattle, lean hogs, pork bellies, lumber, S&P 500, Russell 2000, Nasdaq 100, several foreign currencies, eurodollars
New York Mercantile Exchange (NYMEX)
The NYMEX is best known for trading energy contracts and metals.
Active markets traded: crude oil, natural gas, heating oil, RBOB unleaded gas, gold, silver, copper, platinum, palladium
ICE Futures U.S. (ICE)
The ICE is popular for trading the softs markets.
Active markets traded: sugar, cotton, cocoa, coffee, orange juice
You can trade any of these markets through an account at any commodity brokerage firm. Each exchange publishes information on the markets traded at their exchange, including quotes and charts.