An editorial on MacObserver has an interesting round-up of newer UI metaphors seeing some traction, and some that are a bit futher out there. The author, John Kheit, links out to a ton of interesting content including videos, prototypes, and research papers discussing topics ranging from “wobbly-window UIs” to the much-further-out-there brain implant interface.
The current state-of-the-art User Interface (UI) we've been enjoying has remained largely stagnant since the 1980s. The greatest innovation that has been recently released is based on video card layering/buffering techniques like Apple's Expose. But, there is a large change coming. Rev 2 of the UI will be based on multiple gestures and more directly involve human interaction.
Personally, I have yet to be convinced that many of the ‘UI of Tomorrow’ concepts I have seen or read about would offer a real improvement to the usability of our computers. For example, the UI Tom Cruise used in Minority Report looks like a better way to get a solid cardio workout than do data mining.