Barnard students definitely subsribe to the belief that "busyness is happiness." Most everyone here is juggling at least her courseload, a job, and a club, and that's at the very least. People just want to do everything! Surprisingly, the women here are really on top of their stuff- they get their work done, go to their activities, and have social lives, and even sometimes get sleep (sleep is usually the first thing to go among these things). Write a book if you get through four years here without pulling an all-nighter - I'll buy it! I'll pay you a million dollars for it!
I've had great experiences getting involved in performance groups on campus. My freshman year I was in an a cappella group, and first semester of my sophomore year I was in the CU Musical Theatre Society's production of Into the Woods. Columbia theatre is a ton of fun with many traditions of student run/created productions. I meet most of my friends through my activities, where I live, and my classes- I know how shocking that must sound! I think it's important to always branch out and try new things in college- your spare time is so precious, and you have to really discriminate who and what you give it to. It's not like high school where you had to feel married to a club for four years- you can dabble around in a lot of different things and everyone will still love you.
As for dating, a legitimate concern for prospective students who don't aspire to be nuns: the opportunities are there, even though it's a women's college. All the clubs and activities are mixed with Columbia, so there are always strapping young men around (and by strapping young men I mean, well, at least a pre-screened dating pool... at least you know they're smart!) Do not blame the school for your love life- or do, if it's convenient and your mom is continually reminding you that she met your father in college. It completely depends on your personality. If you liked dating boys in high school and are comfortable with yourself, that won't suddenly change when you get to Barnard. However, if you find yourself tempted to block out relationships and their complications, it is all too easy to do that here. This can be good and bad, depending on your state of mind. But if you want to meet someone, it's not that different from being at a co-ed school- the first thing you have to do is leave your room.
And finally, the weekends. I want to start this by saying I only wanted to go to college in a city, because I was absolutely positively certain I did not want to be in the middle of nowhere with nothing to do but get drunk (beer guts don't become me). So, problem solved, I'm in New York. There are always a million things to do, for free or for a lot of money. You can go downtown and get student rush tickets to a Broadway show, hit up a museum (for free with your student ID), attend one of the many special events in the city- read Time Out New York to see what's going on! There are always events on campus on the weekends- parties, performances, you name it- so if community is what you crave, fear not. The nice thing about Barnard is that while you are allowed to have parties in off-campus suites (not really in the quad, but you wouldn't want to in your little room), most of the parties are at Columbia, so you can go have your fun and then return to the quiet sanctity of your room.