- SuperCoups - http://www.advo.com/consumersupport.html
- ValPak - http://www.coxtarget.com/mailsuppression/s/DisplayMailSuppressionForm
- DMA’s Mail Preference Service - https://www.dmachoice.org/MPS/mps_consumer_description.php
- Five Toll Free Calls to Limit Junk Mail [I particularly recommend the number to stop unsolicited credit card offers] - http://www.timeatlas.com/mos/5_Minute_Tips/General/Five_Toll_Free_Calls_to_Limit_Junk_Mail/
- GreenDimes [I haven't really checked these guys out, so this isn't an endorsement] - http://www.greendimes.com/
Update: If you live in an area where you get weekly fliers in the mail from GlobeDirect (perhaps just the Boston area - since the company is associated with The Boston Globe), I discovered that you can call the number listed on the front of the outer flier (508-871-1900 for me at least) and request to be taken off of their mailing list. Since they normally send out materials once a week, this should make a huge difference!