<p>Art of Problem Solving (AoPS) Community hosts one of the largest online forums for competitive mathematics students, with dedicated sections for AMC, AIME, USAMO, IMO, MATHCOUNTS, and national olympiads including Singapore's. Participants post solutions, ask questions, and access threads spanning decades of past competitions. A complementary resource to the AoPS Wiki and the Alcumus adaptive practice engine.</p><ul><li>Free to read; a free account unlocks posting, voting, and private messages.</li><li>Forums are organised by age band (Middle School, High School, College) and by contest series (AMC 8/10/12, AIME, USAMO/USAJMO, international olympiads).</li><li>LaTeX-enabled posting for mathematical typesetting.</li><li>Also hosts daily problems, contest archives, and community-run mock competitions.</li><li>Self-paced — use actively during contest preparation or casually for problem discussion.</li></ul><p>Create a free account at artofproblemsolving.com to begin posting and following threads.</p>