http://icpcres.ecs.baylor.edu/onlinejudge/
UVa Online Judge site

http://icpc.baylor.edu/
Official International Collegiate Programming Contest (ACM) site

http://www.oi.edu.pl/
Polish Olympiad in Informatics

http://www.soi.ch/
Swiss Olympiad in Informatics

http://acmsolver.org/
ACM-ICPC International Collegiate Programming Contest Training Web Site

http://ipsc.ksp.sk/
Internet Problem Solving Contest - Comenius University

http://www.cs.uleth.ca/~cheng/icpc.html
ACM Programming Contest at Lethbridge

http://www.informatik.uni-ulm.de/acm/
ACM Programming Contest at the University of Ulm

http://get-me.to/oi/
Homepage of Zeyuan Zhu, devoted to programming contests