Not Yet Rated
Watching This Film Is Not Yet Rated makes me want to watch as many NC-17 movies as I can. Honest (and some not-so-honest, as in the case of Team America) depictions of human sexuality almost always earn a film an NC-17 rating, regardless of all other content. Violence, even extreme or graphic violence, usually only earns a PG-13.
As the film made clear, the ratings system is strongly weighted in favor of the major movie studios. The movie studios heavily influence the ratings of their own movies, and they have representatives on the ratings appeals board. Independent films are assigned the dreaded NC-17 rating with far more frequency than any studio-produced movie. One segment in the movie was particularly illuminating: it showed side-by-side scene comparisons of sexual actions deemed too adult in an independent movie, thus earning that movie an NC-17 rating, while showing the same kind of actions being performed in an R or PG-13 movie produced by a major studio. For example, it was NC-17 for But I'm A Cheerleader to show a girl masturbating through her clothes (no nudity at all), but it was R for Kevin Spacey to masturbate (no nudity) in the shower in American Beauty.
It was somewhat infuriating to watch Not Yet Rated, knowing that free expression and artistic endeavors are being squelched by an anonymous, unaccountable collection of people. I don't know that there's any specific action concerned citizens can take, save maybe watching (and paying for) as many independent films as possible.