Location: Cambridge, Mass.

Industry: Transportation

2007 revenue: $59 million

Inc. 500 rank: No. 327

What it does: Operates a car-rental service in cities such as New York and San Francisco

Expert take:"I like the fact that Zipcar is using technology to disrupt a huge market, that they're going after the most attractive geographical segments, and that they're capturing a young demographic," Dagres says. "The big rental car companies could compete with Zipcar, but it would take a while for them to catch up, and Zipcar has some patents. More likely, one of the rental companies will one day buy Zipcar, or the company will go public someday."