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:
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.
A solution which is turned in in the first 24 hours after the problem is announced gets a chance of winning the "lightning division" price. So watch your calendar...
2004 challenge: program ants' brains - http://www.cis.upenn.edu/group/proj/plclub/contest/
2003 challenge: racecar control - http://www.dtek.chalmers.se/groups/icfpcontest/
AMG: Sadly, these links no longer work.