[RS]: ICFP is the international conference on [functional programming]. They run a non-trivial shootout every year - maybe Tclers should join the race?
The main site is http://icfpc.plt-scheme.org/ where it says:

Problem announced   Friday, June 24th, 9:00am CDT 
Initial entries due   Monday, June 27th, 9:00am CDT 
Revision announced   Saturday, July 9th, 9:00am CDT 
Final entries due   Sunday, July 10th, 9:00am CDT 
  
This year's competition rewards programmers who can plan ahead. As before, we'll announce a problem and give you three days to solve it. Two weeks later, we'll announce a change to the problem specification and give you one day to adapt your program to the new spec. And you guessed it: the second half will be worth considerably more than the first.