摘自 http://www.artofproblemsolving.com

初级数学竞赛辅导 - 适于小学生
Mu Alpha Theta.org hosts past contest problems.
http://www.mualphatheta.org/National_Convention/MAO_Past_Tests.htm

Noetic Learning Challenge Math - Problem Solving for the Gifted Elementary Students .
http://www.noetic-learning.com/gifted

Elias Saab's MathCounts Drills page.
http://mathcounts.saab.org/mc.cgi

中级数学竞赛辅导 - 适于初中学生
Intermediate Problem Solvers
AoPS math contest problems and solutions
Past USAMTS problems can be found at the USAMTS homepage.
The Kalva site is one of the best resources for math problems on the planet.
Past Colorado Mathematical Olympiad (CMO) problems can be found at the CMO homepage.
Past International Mathematical Talent Search (IMTS) problems can be found here
MathProb is a website that presents problems and solutions based by categories and is run by Anirudh.

高级数学竞赛辅导 - 适于高中学生

AoPS math contest problems and solutions
Past USAMTS problems can be found at the USAMTS homepage.
The Kalva site is one of the best resources for math problems on the planet.
Nick's Mathematical Puzzles -- Challenging problems with hints and solutions.
Canadian Mathematical Olympiad are hosted here by the Canadian Mathematical Society.
Problems of the All-Soviet-Union math competitions 1961-1986 - Many problems, no solutions.
Past International Mathematical Talent Search (IMTS) problems can be found here
Olympiad Math Madness - Stacks of challenging problems, no solutions