No SOPA is a new Google Chrome extension that would alert you on web pages operated by companies that support the Stop Online Piracy Act.
The app description:
Be notified if you’re visiting the website of a company that supports the dangerous Stop Online Piracy Act legislation.
When you visit a site of a known Stop Online Piracy Act supporter’s domain name, you’ll see a notice bar at the top of the page letting you know.
Boycott? Nasty letter time? You decide.