There are about 80,000 inmates working for state and federal prison industries.   In the state prison industries, 60,000 inmates upholster furniture, grind eyeglass lenses, sew shirts, produce silk-screened clothing and jeans, butcher meat, and make license plates.   In the federal prison industry, 20,000 inmates make a wide range of products and offer several services including the following: they make clothing, file cabinets, electronic equipment and military helmets; handle reservations for TWA and other airlines, do telemarketing for AT&T and other communication networks; do desktop publishing, digital mapping and computer-aided design work; and repair copiers.

http://www.itvs.org/shift/prison.html