UPD: Contest over. Did you participate?
Online Physics Brawl will take place on November 30th. Registration is possible until November 28th.
It's a team competition intended for secondary school students from
Yugoslavia Czechoslovakia Czech Republic and Slovakia, but there's a category for foreign secondary schools and an open category for anyone. Given the target audience, I don't think it'd be impossibly hard for CF users.
You can find the rules and past problems at online.fyziklani.cz. For each problem, you only submit a number, so programming knowledge may be useful (but the problems are fully solvable without it).
I'm a minor problemsetter/tester and the translator this year.