There are lots of ways to show students that gender is a culturally created category, not a biological imperative. One way is to discuss the different agents that enculturate us into our gender roles. If gender is so natural, then why do we have to be taught, from birth, by our families, peers, media, schools, etc., how we are supposed to think/act/be?
After talking about these agents of socialization, I like to show a series of videos that show people playing with gender roles. When students see these unexpected messages coming from the usual media sources, it makes it very obvious that normally we are bombarded by the same message, day after day.
Here are some interesting options:
Girls on Film has re-makes of movie scenes where women play male characters. The Star Trek scene is pretty good. The scene from The Town makes the point better, I think, but is too raunchy for my students' ears. (I'm still trying to live down the great whitewashed willie debacle). What we really need, though, are Boys on Film. Imagine re-making movie scenes where men play female characters. I think it would make it very clear that women, increasingly, can stretch gender roles, but men cannot.
Kaltura's gendered advertising remixer allows you to play the video from a boy or girl's toy ad, while playing the audio from an ad aimed at the other gender. The contrast is pretty striking.
There are a couple wonderful YouTube videos that create gendered messages through music in a way unintended by the original artist. I love the all-female Cornell a capella students group version of Dr. Dre's "Bitches ain't shit." (I've never heard the original of that song, but let me tell you, the title is one of the least offensive lines.) Watching young, affluent women, dressed in country-club style (with tennis rackets), singing a song like that is both hilarious and a fascinating play on gender. Unfortunately, I've never had the guts to show it to a class, because the lyrics are so horrific.
A cuter, and much more class-safe option is the gay remix of Taylor Swift's You Belong with Me. In this video, the "tomboy" girl is a man, in love with his neighbor. It's a very sweet little song/story. But, it still gets the point across, and makes you think about the lyrics and gender roles portrayed in a different way.