
In hot areas, if you have west-facing windows use window tints, blinds, deciduous trees or trellises to help keep out heat from the summer sun. In general, you will lower your summer air-conditioning bill by planting trees and bushes along the west side of your home.
Think of new ways to reuse every day household items, rather that just throwing them in the trash. Use cloth napkins and towels rather that paper towels; use refillable pens and pencils; use rechargeable batteries. Donate reusable items to a thrift store (Women In Need or Nearly New); get together with your neighbors and have a yard sale (make some cash!); advertise your stuff on freecycle.org or ebay.
Keeping stuff out of landfills (or worse, roadside ditches) is good sense. See what happens to our land when we throw stuff away: www.trashedmovie.com
If you have leftover building supplies you'd like to donate to a good cause, you can donate to Habitat for Humanity at http://www.habitat.org/env/restores.aspx.