Anyone who uses 9gag (http://9gag.com/gag/1114501), imgfave, tumblr, youtube, facebook, chive, reddit, photobucket, livejournal, thepiratebay, megaupload (websites based on user generated content), etc. should check out http://www.youtube.com/watch?v=JhwuXNv8fJM to become informed on SOPA, and fill out the form to email Congress (inside US) or sign the petition (if outside US) at americancensorship.org. These sites could be blocked in the US if SOPA passes, because of the possibility that site users may upload/share material that infringes on various copyrights; lack of due process could allow DNS takedowns of sites without notice. SOPA doesn’t only affect websites, but could affect things like email (email providers could be forced to sensor links sent/received) and search engines (links for results could be censored based on content), so this is a HUGE deal.
This doesn’t only affect Americans, but is an international problem, as it will affect American based sites (for example: reddit, youtube, facebook, chive, tumblr etc), and they will no longer be accessible to international people. The vote in the House is on December 21, 2011.