List of Problemsets

Online judges with (mostly) ACM problems

 * UVa Problemset - http://acm.uva.es/p - The Valladolid University Online Judge. Over N problems, for a reasonable value of N.  The problems are culled from old contests, and online contests.


 * ACM-ICPC Live Archive - http://acmicpc-live-archive.uva.es/nuevoportal/ - The 2000's ACM-ICPC Live Archive Around the World. Contains actual problems from regionals and finals from 2000 on.


 * Sphere Online Judge - http://www.spoj.com


 * Zhejiang University Online Judge - http://acm.zju.edu.cn


 * Timus Online Judge - http://acm.timus.ru


 * Saratov State University Online Contester - http://acm.sgu.ru


 * Peking University Judge Online of ACM ICPC - http://acm.pku.edu.cn/JudgeOnline


 * El Judge Online MIPT programming contest - http://acm.mipt.ru/judge


 * Programming Challenges - http://www.programming-challenges.com


 * Arbiter - http://acm.sharif.edu - Sharif University's Online Judge System


 * National Taiwan University Online Judge -http://acm.csie.ntu.edu.tw/ntujudge/index.php


 * Handzhou Dianzi University Online Judge - http://acm.hdu.edu.cn/


 * Zhejiang Gongshang University Online Judge - http://acm.zjgsu.edu.cn/JudgeOnline/


 * Temporary INFOR Online Judge - http://tioj.redirectme.net:8080/JudgeOnline/


 * Open CS Online Judge and Computer Science Community - http://www.open-cs.net

Programming contests

 * IOI - International Olympiad in Informatics - http://olympiads.win.tue.nl/ioi/, http://www.ioinformatics.org


 * MIT BattleCode Competition - http://battlecode.mit.edu


 * TopCoder - http://www.topcoder.com - Quasi-weekly programming competitions from algorithms to components to marathons.


 * URI Online Judge - http://www.urionlinejudge.com.br/ Programming contests on regular basis


 * USACO Contest - http://ace.delos.com/contestgate - Monthly contests (Nov - March)


 * Z-Trening - http://www.z-trening.com - Few contests every month.


 * Canadian Computing Competition - A two-stage annual olympiad. For solutions up to 2015, see this categorization of past Stage 1s by topic. For more recent problems (with some solutions) along with those used in the second stage of the competition, click here.


 * IPSC - http://ipsc.ksp.sk


 * BitWISE - http://www.bitwise.iitkgp.ernet.in


 * CodeCraft - http://felicity.iiit.ac.in/codecraft/


 * Challenge24 International 24-hour Programming Contest - http://ch24.org


 * SPb IFMO Training Sessions - http://neerc.ifmo.ru/trains/ (Note, all problems appear to be in Russian)


 * UPC2001 Internet Contest - http://contest.psu.ru/Inet (link currently broken)


 * Moscow SU Virtual Contests (in Russian) - http://acm.msu.ru/virtual


 * Al Zimmermann's Programming Contest - http://www.recmath.org/contest/index.php


 * Inscription - http://inscription.nitk.ac.in


 * South African Computer Olympiad - http://olympiad.cs.uct.ac.za/old/ - Archive of finals and IOI training contests


 * CodeChef - http://www.codechef.com - Ongoing monthly algorithm programming competitions and short weekend challenges with prizes. Also has practice problems ranging from easy to hard.


 * Alkhwarizm - https://iws60.iiita.ac.in/alkhwarizm/


 * Codecracker - http://codecracker.mkti.in


 * Codeforces - http://codeforces.com

Other

 * Panda Online Judge - https://pandaoj.com - Contains hundreds of competitive programming problems, also acts as virtual judge for other online judges, have helpful features for users.


 * URI Online Judge - http://www.urionlinejudge.com.br/ Programming practice site for students and teams with several problems divided into 8 categories covering several programming subjects


 * USACO Training - http://ace.delos.com/usacogate - "Training" site for the USACO project


 * Project Euler - http://projecteuler.net - Project Euler consists of challenging mathematical or computer science problems.


 * Open Source Instititute - http://www.osix.net - Increasingly difficult "programming puzzles" to solve, including steganography, cryptography and plain-old algorithms.


 * Python Challenge - http://www.pythonchallenge.com/ A series of cute puzzles to solve. You don't have to use Python (but some problems reference specific Python libraries)

Social Programming Networks

 * Fudge - http://fudge.fit.edu - Compute, compete and connect on the world's first social programming network.