I've found a place that will get you taken off both mailing and call lists from marketers ... www.the-cma.org
Otherwise, I also resort to the "please remove me from your call list" when the telemarketers catch me in the middle of doing nothing or finding a 1-800 number on the piles of junk mail I've begun receiving again. I heard of someone sending junk back to folks in those prepaid return envelopes.
Alas, it will never end.