As for me, I was a huge, huge, HUGE band geek in school. I was in the marching band and pep band (I played trumpet)--I was even drum major my senior year, which was totally fun and surprisingly hard. Gee, I wonder why people my age didn't want to listen to me boss them around. haha
I was also in the French club--we didn't really do a whole lot, except make crepes. Mmmmm, crepes...
Other than that, I didn't much after-school stuff, except for participate in the school musicals/plays (either by acting, or by playing trumpet in the pit orchestra). I'm soooo not athletic, so I didn't do sports. Trust me, it was safer for everyone that way.
What about you? Did/do you participate in extracurricular activities?