The Unitarian Universalists are ahead of the pack in working on issues of what we can do personally and congregationally about global warming and environmental stewardship. They have a program called Green Sanctuary to make churches more environmenally responsible. You can download a pdf for a Green Audit for your church. It is a checklist of programs to implement to make your congregation more eco-friendly and have less of a negative impact on the earth.
Another program for churches is an ecumenical program called Restoring Eden. Green Up Your Lent has lots of ideas.
One idea is about fasting:
Fasting generally -- when it takes ten fossil fuel calories for every food calorie in America, eating less can make a big difference!
Fasting from meat -- the second most effective creation-care lifestyle change we can make.
Fasting from dairy
Eating only organic and/or local food
Not using any paper (well, besides toilet paper)
Don't drive (or don't drive alone)
Save electricity by abstaining from TV or video games or blow dryers or microwaves or... you get the idea.
The Episcopal Church has a Committee on Science, Technology and Faith. Their web site has the Catechism of Creation and other links.
Episcopal Ecological Network is another resource for ideas and a e-letter for updates.
Another website is Green Faith - a New Jersey interfaith action group, providing inspiration and ideas and actions for the earth.