Flashblock: Flash blocker for Firefox stops Flash popups

Many sites have turned to Flash as a means of circumventing popup-blockers and selective ad-blockers, relying on the fact that most browsers don't have the ability to turn off Flash on a per-site basis. If you've got a popup blocker installed but still see popups, that's why.

Flashblock is a Firefox/Mozilla extension that provides easy and free Flash blocking on a per-site basis so that you can keep Flash switched on in Flickr, but turn it off for sites that use it to spawn popups. Link (Thanks, Doug!)