Striving to be Green is great, running Green in the Linux world is a bit of a hassle but can be done.
I don't have the time to explain in great detail, but I am going to provide some links to help you on your quest for a "Greener Linux"
Great write up on the usage of CPU-Freq utils:
Thinkpad Linux mailing list- An valuable resource for those with Thinkpads / Ideapads && Linux
Thinkwiki - Another great resource for Lenovo/IBM notebooks and Linux:
Less Watts - Saving power with Linux and Intel:
PowerTop Mailing List:
Hopefully those links will keep you busy for a bit and help you reduce YOUR footprint on the world...