Competitions

American Mathematics Competitions - Organization that administers the AMC, the AIME, and the USAMO, with information about the contests, math problem archives, recommended reading lists, and other resources for students interested in mathematics.
www.unl.edu/amc/

Australian Mathematics Trust - Sponsors a number of competitions in the Australian continent.
www.amt.canberra.edu.au/

Crux Mathematicorum with Mathematical Mayhem - Problem-solving journal at the senior secondary and university undergraduate levels.
journals.cms.math.ca/CRUX/

Math Competitions in USA - Sample problems, information and links from multiple contests.
www.albanyconsort.com/contests/contests.html

Mathematics Archives - links to contests, problem sets, journals sites.
archives.math.utk.edu/contests

Putnam Exam Information - Results from the Putnam competition, old exams, and problem archives. Includes problem of the day, selected from over 540 different Putnam, National or International Olympiad problems.
www.math.harvard.edu/putnam/

Valentin Vornicu's MathLinks - Math Olympiad Problem Solving site with a weekly contest, resembling IMO in difficulty, with a large math forum and downloadable materials.
www.mathlinks.ro