My mother-in-law was the queen of catalogs. She had stacks of magazines and mail-order guides on every end table. Not anymore. Since going greener, she's canceled a bunch of subscriptions, and yesterday she let us know about Catalog Choice, a website where you can sign up for a "do not send" list. You choose who can and can't solicit you, and it takes about 15 minutes.
You sign up using your email and mailing address, then go through a list of catalogs and select which ones you want to cancel. It's free, but it can take up to ten weeks to stop receiving junk catalogs in the mail. If you've canceled a catalog and are still receiving it, you can report the problem to Catalog Choice and they'll follow up with the vendor to stop the solicitation. To see their privacy policies, you can click here.
(Thanks for the tip, Colleen!)