I'd stay away from exit pop sponsor programs because I HATE how they pop up a million windows when someone exits.
If you were thinking about something like that, what I'd recommend doing, is what I do. Make up a popup window and put in some links to some sponsors and/or some of your top referrers, so you only have that one pop, which most people can live with.
One other option would be to join a program like
http://www.http://www.totally4freecash.com they have this great looking full size window that you can use for an exit pop and make 3 CENTS PER CLICK ! It's run by the great people at NexCash, so you'll get paid. They also have 2 new niches coming up.
Here's what their window will look like and like I say, it only pops once, so that's VERY nice. I use this on a couple of my sites. Here's a smaller view of the pop
<img src=http://www.totally4freecash.com/images/smallfpad.jpg>
[This message has been edited by Slick (edited 09-23-2001).]