In honor of Earth Day, Retrevo, a site specializing in consumer electronics info, put together a PDF guide with a lot of good info about the environment and electronics.  Here are some tips from Retrevo's guide on how to be greener when using your electronics:

1. Turn off devices when you’re not using them – especially game consoles and TVs.
   Large plasma TVs are the biggest hogs but game machines are a close second.  Shutting down game players in the U.S. for just 24 hours would save enough energy to power the city of San Diego for a day.
    
2. Make sure they’re really off – use a power strip and flip the switch.
   Many products draw power after they’re turned off. If the charger in the wall socket is warm it's likely sucking power. Use a power strip and shut it down to insure gadgets are really off.
    
3. If you’re going to leave your computer on, at least set them to Hibernate or Standby.
   Energy Star says the PC’s Hibernate or Standby mode can save up to $75 a year in electricity. And, don’t be fooled by screen savers – they’re no help at all.
    
4. Unplug the gadgets you only use occasionally.
   If you only use them once in a while – fax machines, or peripherals attached to your computer such as USB hard drives for backup – unplugging guarantees they’re off.
    
5. Use renewable energy to recharge small devices like iPods, cell phones and GPS.
   Inexpensive devices like the Hymini wind turbine, Solio's Hybrid 1000, Freeplay Freecharge, or Kinesis Industries combo are easy to use and get your gadgets going in minutes.

These hints are all apart of Retrevo's Survival Guide to Greener Living with Electronics.  In this guide, there are more helpful hints, suggestions, and more information about how to live greener when using and buying electronics.