Didn't your mother teach you how to share? If so, you might already have the key to having some wheels without the aggravation of actually owning a car.

While car sharing services have been around in the U.S. since the late 1990s, they've only lately began to really catch on. Today, Massachusetts-based Zipcar is the world's largest car sharing company, with its 275,000 members in the U.S., Canada and London sharing 5,500 cars.

As of January, there were around 24 U.S. car sharing programs, according to Susan Shaheen, co-director of the Transportation Sustainability Research Center at the University of California-Berkeley.

But Zipcar controls the market and has helped advance to concept of car sharing as a convenient way to drive, save money and be green.

Zipcar's Beginnings

Efforts at car sharing services go back as far as the 1940s in Europe, but the roots of car sharing in America can be traced back to 1998, when Dave Brook, an energy-conservation agent for Oregon State University, started up a car-sharing service in Portland, Ore., with four Dodge Neons. The effort eventually grew to two dozen cars before Brook sold the business to Flexcar, a Seattle startup company, in 2000.

Zipcar, which itself started up in 1999, absorbed Flexcar in 2007. From the start, the company did away with lock boxes and log books that other services used, instead taking the operation online.

In nearly 50 cities across the country, including New York, Seattle, Los Angeles and Washington, D.C., Zipcars are parked in small clusters in neighborhood garages.

To reserve a car, you go online, find the nearest location and pick out your car. Honda, Toyota, Mazda, Volkswagen and Volvo are the Zipcar standard-bearers, and the Mini Cooper its signature ride.

To access the car, you wave a "Zipcard" in front of a reader inside the windshield. The program costs $25 to apply and $50 annually. Hourly rates start at $8, with daily rates from $60 -- and that includes gas, insurance and up to 180 miles.

Is It Right For You?

Car sharing isn't for everyone.

According to Shaheen's research, it generally works better in urban areas and for drivers who drive less than 7,000 to 10,000 miles per year. It's also not ideal for daily commuter trips.

If you like things just so or wouldn't dream of lending your own car to a friend, you might want to reconsider as well. While members agree not to smoke, let their dogs loose or leave fast-food wrappers in the car, there will likely be signs others have used the car.

How Much Savings?

Depending on your driving habits, car sharing might allow you to save some green. Sharing eliminates the fixed costs of private car ownership, which AAA pegs at $8,000 per year for a midsize sedan.

"It causes vehicle owners to reevaluate their vehicle usage and whether or not they need to own a vehicle," Shaheen said.

Zipcar also claims to be an eco-friendly alternative to automobile ownership.

"Each Zipcar put on the road replaces 15 personally owned vehicles," said Steve Bishop, general manager of Zipcar Chicago. "Members give up their private cars, drive less and walk, bike and use public transit more often. It doesn't get much greener than that."

Saving Environment, Changing Culture

But you don't have to sell Champaign, Ill., resident Carol Timms on Zipcar or the idea of car sharing.

Timms, an environmental activist and education consultant, signed up for her membership before the company even expanded to the Champaign-Urbana area earlier this year. She uses the cars for errands around town and board-meeting trips to Chicago.

"First comes Tonka Trucks then Hot Wheels," she said. "Before you know it, you're dreaming of a GTO, a Shelby Cobra or a Barracuda. Americans are obsessed with our cars."

Timms is an especially big fan of the Toyota Prius, one of six cars Zipcar has in her area. She said the average Zipcar user saves $500 a month versus owning a car.

"I'm an energy geek from way back," she said. "This is great for the environment. It means a lot fewer people will need to buy cars."

Competition Drives Market

But Zipcar isn't the only car sharing service out there.

Services such as I-Go Car Sharing in Chicago, PhillyCarShare in Philadelphia, and CityWheels Carsharing in Cleveland are just some of the organizations trying to reduce the number of cars on the road.

The effort goes as far as working with cities to ensure private developers incorporate car sharing into planned developments. PhillyCarShare has led the way among non-profits, introducing free memberships, a fleet of more than 50 percent hybrid vehicles and free rides on rail transit for users of vehicles parked at more than 40 stations.

Even car rental companies have gotten into the act, with Hertz rolling out Connect by Hertz late last year in New York, London and Paris, and hinting at plans for rapid expansion.

Robin Chase, a Cambridge, Mass., resident who helped co-found Zipcar before leaving the company in 2003, is also offering her own twist on car sharing that taps into social networking.

GoLoco.org is designed to help people save on gas and cut carbon emissions by helping them find rides. In other words, true car sharing.

GoLoco does this by matching people with others going their way and providing drivers with online tools to collect payment for the costs of providing the ride, such as gas and vehicle wear and tear, with a few mouse clicks. GoLoco collects a 10 percent transaction fee to fund the site.

"My goal is to reshape the way people feel about car ownership," Chase said. "We're going to train people that driving alone should make you feel lonely and pathetic. And that sharing a ride with someone is way more fun, you save money and you get an environmental halo."