Below is the most comprehensive list of OJ:
 
Beijing University of Posts and Telecommunications http://acm.scs.bupt.cn/onlinejudge/ (recommended)
Peking University http://acm.pku.edu.cn/JudgeOnline)
 
Http://poj.grids.cn/(internal)
 
Zhejiang University http://acm.zju.edu.cn/(recommended)
 
Tianjin University http://acm.tju.edu.cn/toj/
Sichuan University http://acm.scu.edu.cn/soj/
HKUST http://acm.ustc.edu.cn/
Harbin Institute of Technology Co., http://acm.hit.edu.cn/
 
Http: // 202.118.224.210
 
Shantou University http://acm.stu.edu.cn/
Wuhan University http://acm.whu.edu.cn/oak/
Felioj http://acm.whu.edu.cn/felioj/
East China Normal http://acm.cs.ecnu.edu.cn
Xiamen University http://acm.xmu.edu.cn
Hangzhou Electronics Co., http://acm.hdu.edu.cn.
Jilin University http://acm.jlu.edu.cn
Http: // 222.196.33.254/judgeonline/
Harbin Engineering Co., http://acm.hrbeu.edu.cn/
Hunan University http://acm.hnu.cn: 8080/
Fujian Normal http://acm.fjnu.edu.cn/
China Southern Airlines http://acm.nuaa.edu.cn/
Beijing airline http://acm.buaa.edu.cn/
Huazhong University http://acm.hust.edu.cn/judge/
Nankai University http://acm.nankai.edu.cn/
Beijing Normal University Online judge: http://acm.cist.bnu.edu.cn/contest/index.php
Vijos http://www.vijos.cn/(high school student's OJ)
 
Ultraviolet A http://online-judge.uva.es/problemset/
Ural http://acm.timus.ru/
Sgu http://acm.sgu.ru/
Spoj http://www.spoj.pl
El http://acm.mipt.ru/judge/problems.pl
Krsu http://www.olymp.krsu.edu.kg/
Usaco http://train.usaco.org/usacogate
 
A comprehensive classification
Acm oj collection (in no particular order ):
 
Latest online game list: http://www.gccfeli.cn/iac/
 
China: (China)
 
China East:
 
Zhejiang:
 
Hangzhou University of electronic science and technology (HDU): http://acm.hdu.edu.cn/
 
Zhejiang University: http://acm.zju.edu.cn/
 
Zhejiang University of Technology (zjut): http://acm.zjut.edu.cn/
 
Zjnu: http://acm.zjnu.cn/
 
Zhejiang industrial and commerce (zjgsu): http://acm.zjgsu.edu.cn/
 
Ningbo Institute of Technology (NIT): http://acm.nit.net.cn
 
Zhejiang Lin University (zjfc): http://info.zjfc.edu.cn/acm
 
Shanghai:
 
East China Normal University (ECNU): http://acm.cs.ecnu.edu.cn/
 
East China University of Technology (ecust): http://acm.ecust.edu.cn/
 
Tongji University: http://acm.tongji.edu.cn/
 
Jiangsu:
 
Nanjing University of Aeronautics and Astronautics: http://acm.nuaa.edu.cn
 
Fujian:
 
Fuzhou University: http://acm.fzu.edu.cn/
 
Xiamen University (xmu): http://acm.xmu.edu.cn/
 
Fujian Normal University (fjnu): http://acm.fjnu.edu.cn/
 
Anhui:
 
University of Science and Technology (USTC): http://acm.ustc.edu.cn/
 
North China:
 
Beijing:
 
Beijing Jiaotong University (bjtu): http://acm.bjtu.edu.cn/
 
Peking University (PKU): http://acm.pku.edu.cn/
 
Tianjin:
 
Nankai University (naikai): http://acm.nankai.edu.cn/
 
Tianjin University (tju): http://acm.tju.edu.cn/toj/
 
Northeast China:
 
Heilongjiang:
 
Harbin University of Engineering (hrbeu): http://acm.hrbeu.edu.cn/
 
South China:
 
Guangdong:
 
Sun Yat-sen University: http://acm.zsu.edu.cn/
 
Southwest China:
 
Sichuan:
 
Http://acm.swun.edu.cn (swun)
 
Central China:
 
Hubei:
 
Hust: http://acm.hust.edu.cn/JudgeOnline/
 
Wuhan University (whu): http://acm.whu.edu.cn/
 
Hong Kong, Macao and Taiwan regions:
 
Hong Kong:
 
University of Hong Kong (hkoi): http://judge.hkoi.org/
 
Russia: (Russia)
 
Ural: http://acm.timus.ru/
 
Salatov University (sgu): http://acm.sgu.ru/
 
El judge (mipt): http://acm.mipt.ru/judge/problems.pl
 
Spain: (Spanish)
 
Walladud University (ultraviolet A): http://icpcres.ecs.baylor.edu/onlinejudge
 
United States: (America)
 
Usaco: http://train.usaco.org/usacogate
 
Poland: (Poland)
 
Spoj: http://www.spoj.pl/
 
Kyrgyzstan: :( Kirgizstan)
 
Krsu: http://www.olymp.krsu.edu.kg/GeneralProblemset.aspx
 
BBS of major universities in China:
 
Http://acm.hdu.edu.cn/forum/ (Hangzhou)
 
Http://bbs.freecity.cn (Zhejiang University)
 
Http://bbs.tsinghua.edu.cn (Tsinghua)
 
Http://bbs.sjtu.edu.cn (hand in)
 
Http://bbs.fudan.edu.cn (Fudan)
 
Http://bbs.whu.edu.cn (wuda)
 
Http://bbs.zjut.com/(Zhejiang University)
 
Http://bbs.tongji.edu.cn (Tongji)
 
Http://bbs.xmu.edu.cn (Xiamen University)
 
Http://bbs.ustc.edu.cn/()
 
Https://bdwm.net/(Peking University)
 
Http://bbs.nankai.edu.cn/(Nankai)
 
Http://bbs.tju.edu.cn/(day)
 
Http://bbs.sysu.edu.cn/(medium)
 
Http://bbs.whnet.edu.cn/(huake)
 
Others:
 
Http://online-judge.uva.es/board/index.php/ (ultraviolet)
 
Others:
 
Topcoder: http://www.topcoder.com/tc
 
ACM-ICPC: http://icpc.baylor.edu/icpc/
 
Http://www.usaco.org/
 
National Computer Olympics: http://ace.delos.com/usacogate
 
Family of informatics beginners: http://oibh.ioiforum.org/
 
China Education sugon Network: http://www.chinaschool.org/aosai/
 
Fujian informatics Olympics: http://www.cfcs.com.cn/fjas/index.htm
 
IOI: http://olympiads.win.tue.nl/ioi/
 
Efficient informatics online discriminant System (vijos): http://www.vijos.cn/
 
ACM routine and test data: http://www.karrels.org/Ed/ACM/
 
ACM community: http://www.608088.com/