Adblock Plus 0.7.5.4
This is a great firefox extension I have, and it works better than any ad blocker I've ever seen. Its stops all those annoying flash ads that are so popular now too. And you can easily disable it on a site you want it to allow ads as well.
Ever been annoyed by all those ads and banners on the internet that often take longer to download than everything else on the page? Install Adblock Plus now and get rid of them.