You've probably already seen this site, which details a product line best summed up by the brand name: Skycar. Actually making it happen will be a bit tricky (if you thought managing highway infrastructure was complicated, wait till you try managing aerial infrastructure!). Still, it's a great proof-of-concept experiment for those of us with visions of a gleaming future, glass-towered cities, and brushed-aluminum sidewalks suspended in mid-air. (Anyone else remember the "Our New Age" comic strip, by Dr. Athelstan Spilhaus?)