Silicon Valley Toxics Coalition have some good guides.
the greenest energy is the energy you don't use
Buying and using energy-efficient appliances can lead to cost savings; with up to $180 per 1,000 kilowatt-hours of energy, cutting up to 80% off your electricity bill. It can also cut 20-30% off your air-conditioning bill because you are reducing the amount of heat that your equipment generates and that needs to be cooled (DEH 2006).
When your computer can no longer keep up with you, it will be awesome to someone who needs a computer. Donate your computer to a charity or organaisation and help them set it up.
National Recycling Coalition - Electronics Recycling Initative
Contact your local or state government recyling service for details of your local E-recycle centre