I may be late to the party, but I want to highly recommend the Adblock Plus plugin for Firefox. It is free, quick to install, and it blocks virtually all banner and pop-up ads. It’s amazing what a difference it makes. It even blocks ads in things like Hulu. I haven’t noticed any slowdown, and it is easy to add exceptions for sites where you want to allow pop-ups. I will definitely recommend this plug-in to my students, and it would make an interesting discussion topic in a unit on consumerism. Looking at the things we get for “free” (because they serve as conduits for the delivery of advertising) is a great class topic.