I hate to get all political on HN, but I saw this week that Bernie Sanders (a socialist, even) introduced an amendment that would explicitly state that constitutional rights apply only to citizens, not corporations, and also prohibit corporations from making political contributions.

Video: https://www.youtube.com/watch?v=G9qZZVqSQ

Petition page with the complete amendment: http://sanders.senate.gov/savingdemocracy

It sounds like it's too loosely written as it stands (see the WSJ article for a fearful analysis), but it's an interesting concept.