A knitter decided that she was not happy with the amount of plastic shopping bags eneding up in landfills and as litter. She thought that if she made one cotton knitted shopping bag to replace one plastic bag and used it over and over for years, she'd be saving many plastic bags from being used over that time span. Multiply that One Bag by many others made to replace one plastic bag and you have a small grass roots charity movement for the Earth.
Check out the One Bag concept here: http://scrumptiousliving.wordpress.com/2008/07/03/a-little-something-for-the-planet/
Sorry for the old school cut and paste job but the link feature and I are not getting along.