Lifehacker.com has a wonderful post that can help you do just that. Here is one example:
Opt Out of Prescreened Credit Card Offers
- Probably the biggest culprit, unsolicited credit card offers not only clutter the mailbox, but because of the included plastic "sample" card are also difficult to shred. You can opt out of these credit card offers by visiting OptOut Prescreen.com, the official service to be removed from the mailing lists of the consumer credit companies.