How difficult will it be to get into college?

I have a 3.5 GPA, but I'm taking rigorous classes in my school's International Baccalaureate program. I'm involved in two different sports (varsity level) and I am captain of one of them. I also play a musical instrument and have won a few trophies. Oh.. and I've taken up two internships. I am currently a junior and still have a about half a year to go before turning in all my college applications and I was wondering if my GPA would considerably hurt my chances of getting into a considerably prestigious college or university (by considerably prestigious, I am talking of schools such as Boston College, Vanderbilt, Northwestern, etc.).