Check out 41 Pounds  by Grist.org.  You can have your junk mail stopped or severlly limited for five years.

It costs some money – $8.50 per year. But look at what you get in return.  This from their website:

41pounds.org stops your junk mail and catalogs — protecting the environment. Junk mail wastes an incredible amount of natural resources and contributes to global warming. Our nonprofit service covers your entire household for five years, saving…

Time — No credit card offers to shred or unwanted catalogs.
Trees — Keep 100+ million trees in forests, cooling the planet.
Water — Protect 28 billion gallons of clean water.
Climate — Junk mail produces more C02 than 9 million cars.
Planet — We donate to your favorite charity when you sign up.

I just signed up, how about you?