EPA’s Electronics Donation and Recycling website provides information on companies and drop off locations for donating and recycling your old PC, television, or mobile device. "Electronic products are made from valuable resources and materials, including metals, plastics, and glass, all of which require energy to mine and manufacture. Donating or recycling consumer electronics conserves our natural resources and avoids air and water pollution, as well as greenhouse gas emissions that are caused by manufacturing virgin materials.”
Check with your state environmental agency as there also may be state regulations regarding the disposal of computer equipment.
For more information, particularly regarding the Resource Conservation and Recovery Act (RCRA), see the Wastes FAQ Database.