Problem Writing For Mathematics Competitions
- Mathematics problems for middle school and high school math competitions with topics range from algebra and geometry to probability and trigonometry.
- http://www.virtu-software.com/math/

Mathematics Problem Solving
- Old sample problems from Putnam training sessions, by Monica Nevens (University of Ottawa).
- http://aix1.uottawa.ca/~jlevy/putnam/

Madras College Mathematics Department Resources
- Problems from UK Math Olympiads and a collection of training materials.
- http://www.madras.fife.sch.uk/maths/resources.html

Union College Putnam Club
- Problem sets from weekly practice sessions.
- http://www.math.union.edu/~barbanej/putnam/putnam03/

Tournament of Towns at Toronto
- Contest problems and solutions for The International Mathematics Tournament of the Towns.
- http://www.math.toronto.edu/oz/turgor/archives.php

Resources for the Putnam Mathematical Competition
- Three sets of practice problems in PDF format compiled Yang Wang of Georgia Institute of Technology.
- http://www.math.gatech.edu/~wang/putnam.html

Putnam Problem Solving
- Supplementary problems and related links by Byungchul Cha (Johns Hopkins University).
- http://www.mathematics.jhu.edu/bccha/Putnam/putnam-03-f.html

Prof. W. Kahan's Notes and Problems
- Large archive of problems and solutions from Professor Kahan's Putnam Problems Practice Seminar.
- http://www.cs.berkeley.edu/~wkahan/MathH90/

Problem Page
- Archive of problem sets and solutions from Wisconsin Mathematics, Engineering and Science Talent Search.
- http://www.math.wisc.edu/~talent/problems.html

Math Olympiads
- Collection of problem sets from International and National Mathematics Olympiads.
- http://cage.rug.ac.be/~hvernaev/olympiad.html

Kalva
- Complete set of all International Mathematical Olympiad problems with solutions. Also includes problems sets from other national and international contests.
- http://www.kalva.demon.co.uk/

International Mathematical Talent Search
- Solutions and Comments.
- http://www2.arnes.si/~ssdvbens/nsc/imts/imts0.htm