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Going on right now: Fourth Annual Mars Settlement Design Competition:

The game scenario is set in the middle of the 21st century, when The Foundation Society, a fictitious private organization that promotes human exploration and colonization of space, issues an urgent call to industry to propose a design and operating plan for a new Mars base.

The site for the competition is here, complete with Flash intro.

I believe the Orange County or San Diego AIAA section sponsors a similar competition.