While we're on this whole skyscraper kick, how about a wind-powered tower? David Fisher, a French architect, is in the approval stage for two towers—one in Moscow and one in Dubai—where each floor rotates independently of one another, driven by wind turbines fitted in between each floor (which also creates the electricity to power the building, and possibly other nearby buildings as well). And Fisher's buildings will be less expensive to build because the core is all that's built on-site. The rotating pieces will be built elsewhere in a modular fashion, attached to the core and sent up. They'll be built from the top down!
Fisher's company, the Rotating Tower Technology Company, has these two projects on display at its website, and the videos are really quite stunning.