The major credit agencies (Equifax, Trans Union, Experian, and Innovis) all sell aggregate credit information to any bidder. Direct mail and credit companies buy lists based on demographics including zip code, income band and credit payment patterns ... and then mail out to thousands or even millions of "potential customers."  The Fair Credit Reporting Act entitles you to contact to contact these agencies and request they stop seding you card solicitations and related offers.  There are two easy ways to opt out:

• Online: You can go to www.optoutprescreen.com, and fill out very short, one page form electronically that will opt you out for 5 years.  If you want to opt out permanantly you have a print out a form and mail it in.
• Over The Phone: Call 1-888-5 OPT OUT (available 24 hours a day).  All you need to know is your address, former address within two years, and social security number.

Both options will update each of the major credit agencies for you.  It will take a couple months to see the effects from either the online or over the phone request, because the credit agencies have to process the request, update their "opt out lists" ... and then after that time they won't sell your information anymore.  But if a company buys your information the day before they update the list, you might not see their promotion/application until a couple months later ... so you have to be patient, but eventually they should stop coming.