My UU church is in the (very embryonic) stages of trying to gain "Green Sanctuary" status. It's actually more painful than childbirth, metaphorically speaking.
(not really, but it's a lot more involved than I expected)
UU Ministry for Earth - Green Sanctuary Program It's a very laborious process, but I think that for one thing, as it really requires a consitent committment by a majority of the congregation, and because it takes more than one or two weekends to do this, it has the absolute benefit of changing people's *personal* habits, not just "Hey turn the lights off in the church before you leave..."
I do think it's important for churches to "walk the walk" of "stewardship of the earth" or whatever, though.