Have you ever been stuck circling the block waiting for a parking space to open up? The new ParkCirca space-sharing service might make that a thing of the past. Co-founder and CEO Chadwick Meyer told me how he was fruitlessly hunting for a space when he noticed how many private driveways had no cars in them. Why not let the driveway owners make some money from them, and save stress (and gas) for the drivers at the same time?

That's exactly what ParkCirca sets out to do. Driveway owners register when their space will be free and how much they want to charge. Drivers can then use an iPhone application to find available spots near their destination, and book them for the time they need. A typical charge might be $2 an hour, in which case an owner with a space available for just eight hours every week day could make up to $320 a month, without losing a place to park in the evenings or weekends.

As a self-funded startup, Meyer and his team have just launched the service in San Francisco by walking around neighborhoods like the Haight, Cole Valley and Inner Sunset, handing out flyers and talking to people. He says the reaction has been very positive. "There's traditionally been a lot of informal sharing between immediate neighbors. This gives people a tool to organize that, and extend the circle of trust a bit further too." He also finds it remarkable how much has changed in the last decade of social technology, since his service relies on "communication between strangers," requiring coordination that would have been almost impossible until recently.

It's still early days, but with several hundred users after just a week, there does seem to be interest. It also seems a natural complement to a car-sharing service like ZipCar, making your choice of parking spot at your destination as flexible as your choice of vehicle.

Meyer pointed out that there are a lot of secondary benefits to the service too. It gives people a chance to help out other locals, to "be a neighborhood hero," reduces the gas wasted circling the block, and removes the hassle of having to move your vehicle every two hours because of street parking regulations. There's an active trade in garage and private space rentals here in San Francisco, but ParkCirca gives you the chance to park in multiple spots, rather than being anchored to a particular location.

There's no guarantees that their model will work, but as some who has recently moved to the city I really hope it does take off. Meyer is currently looking into raising angel funding to support his mission of "making urban life better for everyone," and I wish him luck.