Seems like green IT in general, and the green mainframe, are on the tip of lots of people's tongues lately. Have a look at these online communities, and join in:
Green IT for growing businesses
The Green Business forum is a new IBM-hosted community where small-to-medium businesses can talk about their issues with IT and energy efficiency.
zJournal is an independent (non-IBM) source of information about the mainframe. The journal plays host to a variety of discussion forums for System z clients -- including specific forums for z/OS, z/VM, Linux on System z, Security and other mainframe-related topics. Some of the contributions have to do with issues of energy efficiency and cost savings.
Have a look at these two online communities, and add your voice.
Other mainframe communities, discussions