Here's another flying car link, called the Terrafugia. This one's a very early stage startup some MIT grads are putting together. Instead of feeding the experimental aircraft market, they're planning to sell it under the new Light Sport Aircraft rules. You can read a short blurb on them here.
From the FAQ, it looks like a very early stage project, still at the point of conceptual design. For instance, they talk about taking bids on an engine. They may need to do that early in the process, because some aircraft engines are air cooled. They're designed to produce power in an airplane which is always moving through the air, so there's always air blowing past the engine to cool it. In a car, where you might be stuck in traffic, an air cooled engine may need some kind of cooling fan or other arrangement. Also, I'm a little concerned about road debris, or just plain old dents and dings from the car in the next space over, hitting the upper outboard section of those folded wings.
On the other hand, it's a really intriguing design and would be a blast for city hopping. One more company to keep on the radar screen. Hopefully they'll have a display or presentation at Oshkosh this year.