I installed the Google Toolbar, which allows you to do google searches right from your browser toolbar (so handy, since I use it all the time).
But it also includes a popup killer, which can be set to block them silently, so you dont even notice it.
I turned off everything but the search and popup killer, so it's very inobtrusive. I also moved it to the same line as the File/Edit/View/etc, so it doesnt take up any additional real estate:
http://toolbar.google.com/T4/?promo=mor-tb-en