The Wikipedia/Internet Blackout of 2011 was one of the most effective grassroots PR campaigns I've seen in recent memory. A lot of people have been complaining and trying to raise awareness of the looming danger of the SOPA and ProtectIP bills, but it was mainly an issue among nerds and public watchdog groups. But when Wikipedia and Google blacked out their sites, that reached the mainstream. When my wife asked me what SOPA was, I knew a historic moment had been reached. But then came a new problem; explaining what all the fuss was about. It's easy to get into a lot of Internet jargon and tech crap, but this video does an awesome job of explaining the problem and it's implications. It does more in minutes than I could ever do in an hour.
UPDATE: Included the actual video so you can actually watch it