The impending singularity for interactivity is going to be brought on by successively more powerful platforms for rapidly prototyping and designing games. You've heard of the big ones, there's MetaPlace from Raph Koster's company, and in its own way, Storytron from the Crawdaddy himself. Mockingbird is a game-making platform oriented toward casual, spatial gameplay. It has limitations, but it also has tremendous potential for social commentary. (Ed's Note: Also consider Gamestar Mechanic.)
...when you Log In or Register. Gives you the ability to post to the forums and your own blog; to rate games and receive recommendations based on your ratings; and to bookmark games for later reference.