There's a website called www.experimentalgameplay.com which encourages people to create quick prototypes of games for fun.
I recently had the pleasure of working with the Experimental Gameplay guys to run a competition to win a summer internship at Heavy Iron. The contestants had about two weeks to make a game based on the theme of "Consumption". Sixteen people submitted games, and from these people we chose two interns for summer internships.
I really enjoyed being involved. The games were great fun to play and the winners are really looking forward to starting. Hopefully we'll be able to do the competition again next year.
I recommend checking out what the experimental gameplay site and playing some of the games there. One important thing that the games demonstrate is that you don't need to have a team of 50 people working for six months to work out whether something is going to be fun. There are some lessons in this for large and small developers.