Mean Girls (2004)
Lindsay Lohan, Rachel McAdams, Lacey Chabert, Amanda Seyfried, Tina Fey, Tim Meadows, Ana Gasteyer, Amy Poehler, Lizzy Caplan, Daniel Franzese, Jonathan Bennet
Watching this movie made me all nostalgic. Remember when Blohan was just the little girl who was in The Parent Trap? Aww, I miss those days.
But this was actually an excellent and highly entertaining film about the cutthroat atmosphere of high school. To be quite honest, I don't remember any girls in my high school being quite as mean as the Plastics were in this movie -- they should have set it in junior high instead, the girls in my junior high were ridiculous. I identified most with Janis, who used to be best friends with Regina George, only to be inexplicably dumped and forever ostracized.
This is a great chick flick to watch with a bunch of girlfriends. Pop some popcorn, do each other's nails and reminisce about your childhood and how much you cared about beig popular. 
This was the first Lohan film I'd seen since The Parent Trap, I think, and after all her offscreen antics I was kind of expecting her to be a terrible actress and the film to suck, but I actually loved it. I liked Janis best, too. I was homeschooled and never really had to deal with Plastic-type antics as a teenager, but Janis reminded me of several friends in college who did, and who were equally awesome despite (or possibly because) of it.