I hate junk mail. It's a waste of paper. The worst type is unsolicited credit card offers because you need to shred them (if you just throw them away somebody may pick them out of your trash and apply for a credit card using your information).
In an effort to reduce the number of offers I receive, I recently used OptOutPreScreen.com to opt-out from lists used by creditors or insurers to make firm offers of credit or insurance that are not initiated by me. In case you're worried about the legitimacy of the website, it's directly linked from the FTC website (which contains other useful information for further reducing unsolicited telemarketing calls, promotional mail and spam emails).
I originally submitted an electronic request through the website, which removes me from these lists for five years, but then hubby & I both sent in a hard copy form (provided by the website) to remove ourselves from these lists PERMANENTLY. I doubt it will complete eliminate all unsolicited offers, but at least it's a start.