Below are some links to camps that former MG students have attended and had good experiences. Let me know if you need any more information.
ACE Quiz Bowl: A summer camp for those of you who can't get enough of quiz bowl. It's a great way to improve your game.
PROMYS : a summer camp for mathematically oriented high school students.
CTY: Part of the John Hopkins Center for Talented Youth. Offers a wide variety of choices
SIG: Summer Institute for Gifted. Offered from Bryn Mawr campus
NYLF: National Youth Leadership Forum. Offers camps in Medicine, Law and CSI, and National Security for high school students
Spark the Wave: For students entering grades 8-12. Spark the Wave empowers youth through educational programs to be great volunteers and community leaders. Offered at Villanova's campus
NSLC: For high school students, the National Student Leadership Conference. Focuses on a variety of topics