Being frugal/environmentally friendly

There are several websites/groups of which I am fond (in assisting to achieve a state of being as above):
Freecycle – you can join this via Yahoo Groups. Basically you list things of which you would like to dispose, and then other people offer to come and take things off your hands.
Book Crossing – you register the book, leave it in a public place (and flag it on the website)and other people pick it up. I’ve not used this to find books, but have friends who are very keen.