The United States of America Computing Olympiad (USACO) is an annual computer programming competition for secondary school students in the United States. It was first held in 1993.
The training pages
The USACO has training pages on its website which are designed to develop one's skills in programming solutions to difficult algorithmic problems. In addition to around 100 problems, there are texts on the greedy algorithm, dynamic programming, shortest path, and many other techniques and algorithms. Enthusiasts find the training pages so useful that people from other countries use them to prepare for their own national Olympiads; those from other countries in fact outnumber U.S. participants.
The Internet competitions
There are four divisions for the six Internet competitions held each year: Novice (easiest), Bronze, Silver, and Gold division (hardest).
To qualify for the Silver or Gold division, one must either do well enough in the qualifying contest, usually held in November, or do well in the Bronze and Silver divisions. The Novice division is for first year computer science classes and is separated from the other three divisions.
These contests are designed to be very hard, as well as have a low average score. That way, the top scorers can be more easily distinguished.
The training camp
The training camp is a week-long program held to determine which four students will represent the American team at the International Olympiad in Informatics, or IOI. Around 15 people are invited to the camp, which is held in late May or early June in Colorado Springs, Colorado.
To qualify, one must be a secondary school student in the U.S., have scored highly on the Internet contests, and be far along in the training pages. At the camp, contests are held in the morning, followed by discussion of solutions. In the afternoon, the students engage in various recreational activities, including Ultimate. There are also a few lectures on different areas of computer science and programming. At the conclusion of the camp, there is a ceremony recognizing the participants, and in particular those who are selected for the delegation to the IOI.
Website: http://www.usaco.org/