About a year ago, I saw this post the mentioned GreenDimes. GreenDimes is a services that stops junk mail. We donated the $15 (which is supposed to plant 15 trees), and then filled out the postcards that were in the packet they sent. Then when ever we received a catalog, I would enter that information on the GreenDimes web site.
Within a few months, we have seen a significant reduction in the junk mail and catalogs that we receive. I would recommend GreenDimes, as it has been working for us.