ProQuo is a free service that contacts websites that manage junk mail databases on your behalf and allows you to remove yourself from on-line databases, many with just a couple of clicks.
For the Direct Marketing Association, it directs you to their website, but you don't have to do any looking to find these sources (many of which we hadn't ever heard of). If it requires you printing and mailing a form, ProQuo will allow you to print the form directly from your computer or save it to your desktop to print later.
How will ProQuo make money? Eventually, they'll make offers available so you can get the types of solicitations you want, but it's in beta at this point, and virtually ad-free. Get it while it's hot!
PS They say it takes about 4 weeks to start to see results and 3 months for it to take a hold because many of the marketing pieces are printed well in advance.