Today nearly every college student has a cell phone and an iPod, but there's one possession that remains rare on many campuses: a car. Due to limited parking, many schools restrict students from keeping vehicles. That forces them to rely on public transportation or to rent cars (which is hard, since many rental-car companies serve only drivers 25 or older). Those inconveniences are creating opportunities for Zipcar, the car-sharing service that's been offering by-the-hour car rentals to city dwellers since 2000.

Zipcar began testing its cars-on-campus concept at MIT in 2002. Today it has rentals at 18 East Coast colleges. Zipcar charges students a $25 membership fee; drivers then pay rates starting at $8.50 an hour or $65 per day, which includes gas and insurance. While Zipcar generally rents only to drivers 21 and older, this fall Wellesley College inked a deal that allows even freshmen drivers behind the wheel. The company's college fleet--it includes the Toyota Prius, Volvo S40, BMW 3 Series, minivans and pickups--ferries students home for holidays, on ski trips or to do errands (read: pick up kegs). Zipcar execs have also noticed the vehicles are often rented for a couple of hours between midnight and 5 a.m. Could Zipcars be serving as a roommate-free zone for late-night romance? Zipcar CEO Scott Griffith says, "I'm not going to go there."