Trivia Trek multicultural challenge question open to students and teachers. Winning submissions and interesting user submissions are posted. ThinkQuest Internet Contest annual contest that challenges students, ages 12 to 19, to use the Internet as a collaborative, interactive, teaching and learning tool. Amanda's Debate Page providing high school debaters with ideas, information, resources, and help. Look here for CX and LD evidence trading, as well as information on other events.
Weekly newsletters supply the debate world with both sides.
Joel Hartman's HS Debate tips and links for debate research. This is by far the best general resource on math for high-school students that I have found. Questions and answers for high-school level math questions are located at this site. You can also ask Dr. Math your own question. If you can't find your answer there, check out the College-level questions and answers.