Perl, Javascript, or Ruby might be worth considering too. If you restrict it to a specific language then the judging will be skewed towards "how well do you kn

Perl, Javascript, or Ruby might be worth considering too. If you restrict it to a specific language then the judging will be skewed towards "how well do you know language X" instead of "how well can you translate the problem into data+algorithms." However, allowing multiple languages might bias the competition into a language rather than a programmer contest. PG has said (somewhere, can't find the ref) that one reason they were able to implement ViaWeb as well and quickly as they did was the language choice - Lisp. The logistics of supporting multiple languages might constrain that decision, of course, but a well-designed API might be more language-agnostic.