Ural State University Problem Set Archive with Online Judge System
http://acm.timus.ru Problem Set is the place where you can find large amount of problems from different programming contests. Online Judge System allows you to test your solution for every problem. Tasks: 100
Bulgarian Olympiad in Informatics & Mathematics (1991-1999)
http://www.math.bas.bg/bcmi/ I heard a few days ago that a web site with most Bulgarian olympiads in informatics (in English) had been updated soon. It is the best one with the tasks from our olympiads. Christian
http://ace.delos.com/usacogate I am pleased to make the first formal announcement of the USACO training pages. Sponsored by the USENIX association, USACO has created 200 hours of instructional material and exercises to assist in training for national and international competition.