There are quite a few out there. The one I like is a shareware one that I purchased. It will quit working after the expiration but it is a good program called "Popup Ad Filter" from Meaya Software (www.meaya.com).

Guard-IE Popup killer is good as is Free Popup killer 1.0 (freeware). Check out

http://downloads-zdnet.com.com/3120-20-0.html?qt=popup&tg=dl-2001