http://www.dmaconsumers.org/offmailinglist.html
This works. If you buy a house or refinance etc., you will need to do it again with the new addresses. I find it works pretty well. Most of the junk mail stopped, then we bought/sold a house and it started up again.
I submitted again with both addresses and the junk mail has been cut way down. Now, if it wasn't for the local crap we get........
Edit: Just read some more, now they are asking for $1 to make it legit. The only time I ever paid for this service was $1 to get deceased names off the list.