Well, everyone NEEDS a pop-up blocker these days because theyre all over the web. I personally suggest PanicWare Pop-up stopper. It stops all popups. Only problems I have had is that it blocks alot of windows in Firefox that I click on. I think its mostly meant for IE.
When I used to use IE, I used a popup blocker called EMS Freesurfer MK II because it was recommended on some show on TechTV. Now, with Firefox, there is a built-in popup blocker so I don't need a third party one. The new IE is pretty nice at blocking most popups, though.