First, you can learn who the good guys/bad guys are:
http://projects.propublica.org/sopa/
then do whatever you can to support/bring pressure on them, maybe by concentrating on Rep. Lamar Smith and Sen. Patrick Leahy, and their constituents first:
http://projects.propublica.org/sopa/S000583
http://projects.propublica.org/sopa/L000174
Slashdot has a good article, if you haven't seen it yet:
http://yro.slashdot.org/story/12/01/18/0834219/ask-slashdot-what-can-you-do-about-sopa-and-pipa
Personally, I wanted SOPA to pass. Then I want Facebook to get shut down. It'll be precisely the motivation we need to push for decentralized DNS, heavy crypto, signatures on all data, and other things that I believe the Internet needs.
Facebook wore out my patience years ago. If they're still in business, it's not because of me. My policy for the past couple of years has been to use Tor and NoScript for all my browsing, clear my cookies every session, and use encryption on all of my data disks.
That still leaves the problem of the world governments overstepping their authority. We made one small victory. Don't get cocky.
My thoughts are at http://xeny.net/why%20I%20am%20not%20on%20Facebook%20any%20more