ExitFuel was one of the first networks (if not the very first one) that started offering exit pop-up programs. Currently it has two pop-up-upon-exit programs: ExitFuel regular and ExitFuel Lite.
The regular ExitFuel program pays $5 CPM -- but there is a catch that you will see only after you test their code. Upon leaving your site, you will see a barrage of pop-up windows er....pop-up with machine-gun speed. I don't remember how many they were when I tested it, because I fleed from the screen in horror, but I think there were like, 4 or 5 of them. So unless your goal is to scare your visitors off permanently, I strongly advise not using ExitFuel's regular $5 program.
Up until April 1 of 2003, their ExitFuel Lite was a much better alternative, paying out $3 CPM for a single popup. However, after April 2003, they increased the Lite program to serve 2 popups, without increasing compensation. After a couple of months of paying out only if the second pop fully loads, they changed this policy in June 2003 to pay out for the first pop (visitors will still be shown the second one, but you get paid even if they close it).
Their stats screens are nothing fancy -- they update once a day and show not much more than the number of pop-ups displayed, pay rate and the grand total. Getting to stats can sometimes be a little slow, but they are almost never down. By the way, since they pay for thousand impressions, they will happily dismiss any remainder at the end of the month, thus not paying you for it. For example, if you displayed 9,878 pop-ups this month, you will only get paid for 9,000. Sucks, but you can lose only three bucks a months max with this nasty gimmick.
They pay on Net45 basis, which is a little longer than most small to medium sized networks, but in almost a year with them they have yet to miss a payment.
While PopupTraffic has a $3.00 CPM exit program that only shows one pop-up per visitor, Exitfuel has traditionally credited webmasters for a higher percentage of their traffic than SIC's program, so if you are not afraid of losing visitors, this will probably bring in more money.
Overall, I recommend their ExitFuel Lite Pop-Up Program. Mostly for its decent payout rate: it pays $3 per thousand of uniques. By the way, you register for each program separately, so register directly for ExitFuel Lite. 2 stars for this one (down from 3.5 when EF-Lite was limited to one pop).
ExitFuel 
