has an article about 51 things you can do to save the environment.
Here are my two proposals:
1. Install an air vent opening in your dryer exhaust. Your dryer vents hot air to the outside. In the summer, great. In winter, it's a waste of hot air. A simple Y joint that allows you to vent the hot air into your house in winter will save on heating bills. And the place will smell like fresh laundry.
2. If you live in an apartment building, put a large carboard box downstairs for people to put reusable packing materials. Plastic peanuts, bags of air, foam, bubblewrap: why have to buy it when your neighbor just got a bunch of it?