Here are some useful math-related websites.

Five College Mathematics Departments

• Mt. Holyoke
• Amherst
• University of Massachusetts
• Smith
• Hampshire (Natural Science)

Mathematics Organizations

• American Mathematical Society
• Mathematical Association of America
• Association for Women in Mathematics
  • AWM Mentor Network

History of Mathematics

• St. Andrews archive

Mathematical Encyclopaedia

• Eric's World of Mathematics

Information about the Putnam Contest

• General information
• An archive of problems and solutions