I may be slow to this, but I just discovered the Google Toolbar's anti-popup feature. It will deactivate the onUnload javascript function, which won't eliminate all pop-ups, but it will get those annoying ones that happen when you're trying to leave somewhere. (To get to the feature, click on the Google logo, go to Toolbar Options, and then Experimental Features. [screenshot]. There's some other interesting stuff there, too.)
