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Canada / USA Mathcamp
A summer camp for mathematically talented and mathematically gifted high school students from around the world. It includes advanced mathematical topics not normally covered in high schools.
http://www.mathcamp.org/
HCSSiM
Hampshire College Summer Studies in Mathematics for mathematically talented high school students. 2004 session: 4 July -- 14 August.
http://www.hcssim.org/
MathCamp
MathCamp is a classroom-focused mathematics resource for teachers on the elementary, middle and high school levels.
http://www.mathcamp.com/
PROMYS
The Program in Mathematics for Young Scientists: a six-week summer program at Boston University.
http://www.promys.org/