This is from wikipedia:
Chicago Climate Exchange (CCX) is the world’s first and North America’s only voluntary, legally binding greenhouse gas (GHG) reduction and trading system for emission sources and offset projects in North America and Brazil. A project that is beyond business as usual is commonly referred to as a carbon project. CCX employs independent verification, includes six greenhouse gases, and has been trading greenhouse gas emission allowances since 2003. The companies joining the exchange commit to reducing their aggregate emissions by 6% by 2010. To date the exchange has more than 120 members ranging from corporations like Ford and Motorola, to state and municipalities such as Oakland and Chicago, to educational institutions such as Tufts University and University of Minnesota, to farmers and their organizations, such as the National Farmers Union and the Iowa Farm Bureau. CCX has an aggregate baseline of 226 million metric tons of CO2 equivalent, which is equal to the United Kingdom’s annual allocation under the EU ETS. This would make CCX one of the largest “countries” in the EU CO2 market, or 4% of U.S. annual GHG emissions.

Bank of America has recently added itself to the list of companies who have volunteered to cut down on emissions.
According to Market Watch: Bank of America (BAC :
47.13, -0.80, -1.7% ) and Climate Exchange PLC announced that Bank of America will become a member of the Chicago Climate Exchange, the world's first voluntary emissions exchange with a legally binding greenhouse gas reduction registry and trading program.
Bank of America has also committed to join the Chicago Climate Futures Exchange and the European Climate Exchange.
The Charlotte, N.C., bank will also form a joint venture with Climate Exchange, in conjunction with Bank of America acquiring about 0.5% of the current issued share capital of Climate Exchange.
Bank of America will also develop, market and execute new environmentally focused products using CLE-linked offsets, which are credits used by individuals and corporations to reduce total carbon footprint.