Annual computing-science competition for talented senior high-school students. Contains links to the homepages for every year and status information about the organisation of the event. http://olympiads.win.tue.nl/ioi/
An official site describing the history of the contest, official regulations, future locations and members in many countries of the world. http://www.ioinformatics.org/
An annual computer programming competition held at Dublin City University, sponsored by DCU and IBM Ireland, for pre-university programmers. http://www.compapp.dcu.ie/~cdaly/ire_comp.html
USACO supports pre-college computing around the world through computer programming competitions and training materials. Site contains details about current and previous competitions, alumni, training, and registration. http://www.uwp.edu/academic/mathematics/usaco/