Here is a good idea I just ran across at Vertical Response Marketing Blog.
This business card from Birdy Botanicals has a message 
on the back offering a 25% discount
off your next purchase if the prospect signs up for their
newsletter. Comment if you like this idea
or if you have a similar idea. Or if you have a similar example.
You may have a wonderful weblog. I’ve read a number of of the posts and enjoyed them. I will probably return.