I used to have a very unpleasant viewing experience on various sites due to annoying ads, until my sister recently pointed me towards adblock plus. It's not perfect (very few ads still slip through), but it's pretty darn close. Good job.

Unlike Adblocker Ultimate, it doesn't break tumblr and mediafire. However, it has it's own annoying pop up messages appearing in my browser, which is both ironic and annoying for something that supposed to block things like annoying pop-ups.