My mother, who has a lot of friends that send her hoaxes, email chain letters and other forms of internet tomfoolery on a regular basis, got an email from 41 Pounds. 41 Pounds claims that they will stop your US Postal junk mail if you give them money.
I cannot tell if these are legit or not; Doing searches on the internet are largely self referential. The problem with this kind of service is that they could, in theory, sign you up for the Direct Marketing Association’s do-not-mail list and stop there. You would notice a decrease in mail and everything else they could say, “Well, we stopped a whole lot. We can’t be perfect.” How could you tell?
The best way to ensure that you don’t get any more junk mail is to do it your self. You’ll know what happened, how to do it again, and if you want to give money to charities you can do that directly.
[Added 2007/05/05] Here are two Greendimes admin interface images: