Additionally, you could also boycott all the products of SOPA backers such as the MPAA or RIAA.
Unfortunately, every time I try to explain to my friends that I don't want to see a Pixar movie and would rather see a movie at an indie theater instead, no one seems to really understand what the problem with Pixar or Disney or Sony or UMG is.
It turns out, almost no one cares about the DMCA or SOPA or Protect-IP or anything that requires more than 30 seconds to explain. It is quite depressing...
Unfortunately corporations have become the new governments/armies, and so if you boycott every corporation that does something you don't like... you're screwed.
It's like telling people in Soviet Russia that if they don't like Communism, they should boycott the communist food lines. It's an unreasonable request. The free market is no longer free, corporate oligarchies might as well be called Soviet Planning Committees. (What the Soviets called their authoritarian overlords who owned and distributed all the resources)