The latest snail mail experiment i tried didn't quite meet the target response rate. Only had a 1:40 response - i'm putting this down to a dodgy database supplier though, as the demographics of people in it where way off compared to data i fully trust. The campaign consisted of a letter with a unique "Access Code" linked to each person, which they had to type in to enter the site. Will be doing more along those lines in the future though.
Other campaigns with CD's are getting a 1:15 -> 1:25 response, which is fine
I would be very interested in working with Adult DVD suppliers on some direct snail mail marketing to some of my old member data etc.