Take a look at studentcompetitions.com for some excellent competitions for high school and college students. Categories listed include Business, Arts & Design, Social Studies, Tech & Engineering, Natural Sciences & Math, and Other Events. Students can sign up to receive a bi-weekly newsletter, schools and other organizations can upload their competitions, and students can become Global Ambassadors. Searches for competitions can be done by keyword, group (high school, college, MBA, etc.), by deadline, or by prizes offered.