My roommate came across this website when he learned that I wanted to be a game designer. I thought it was a really cool concept. They post a game design theme, and people submit game designs. They then select the best few game designs, and post the winners. While I haven’t submitted any game designs yet, I look forward to possibly having some time in the summer to more thoroughly investigate this site.
If I’m not mistaken, the link above links to this week’s current design challenge. The link to the site that contains these challenges can be found here. Just click on the current game design challenge (It’s currently the first major link).