Will Wright, the inventor of SimCity and the Sims, is working with Maxis to develop Spore, a game that takes the "Sim" concept to a monumental scale. The game begins with you controlling the first single-celled organism and you manipulate species, evolving creatures until you finally have created a race of intelligent, space-traveling beings. The developers claim that the technology powering this game will create scenarios with a vast scope and endless possibilities. If you have ever wanted to play god, now you can. Expect this game to be released sometime in 2008 for Windows, Max OS X as well as spin-offs for the Nintendo DS with a creature phase game and Mobile Phones, including the iPhone with a tide pool phase game.
A recent demo of Spore can be found here.