There are lots of pop up advert removers out at the moment, obviously reflecting the widespread distaste that most people have for this kind of intrusive advertising. Free Surfer is a free pop up advert remover that is nicely designed, works well and is very unobtrusive (which to my mind is the sign of a good software utility). It was also recommended by the inimitable Chris Pirillo at Lockergnome, which is in itself a good sign.