In urban planning and environmentalist circles, living in high density urban neighborhoods is desirable. But as any Manhattanite (or San Franciscan) will tell you, such a lifestyle comes with trade offs – small living spaces (with no guest rooms), high rents, no yards, and no trips to the countryside (or the megamart) with your car.

Fortunately, a number of new tech powered tools and services aim to address some of these drawbacks, by allowing neighbors to share household tools, cars, and even backyards.

First up is NeighborGoods. The newly launched site provides a place for people to list any items they are willing to lend – either for free or a fee. Visitors can easily search for various items in their vicinity (perfect if you want to borrow a lawn mower or a sewing machine), and the site provides some conflict mediation system in case someone doesn’t return an item.

Borrowing a power drill is one thing, but borrowing a car? The new peer-to-peer car sharing service RelayRides promises just that. Modelled after commericial car sharing services like Zip Car, RelayRides allows anyone who owns a car to loan it to their neighbors – at their specified price. The site takes care of insurance, and provides a smart card reading device to permit borrows to access cars. Launched in June and currently only available in Cambridge, Massachusetts, the company hopes to expand to other cities.

Finally, with all the focus on locally grown food, it makes sense that someone started SharingBackyards.com. And given that a full 40% of North Americans do not private yard space, and the other 60% often isn’t using it fully, the site seems poised for growth. Working with partners — such as Garden Swap in Los Angeles, CA — the site works by linking people with unused yard space with those looking for a place to grow food. All you have to do is enter your address.

While many of these services are still in their infancy, they point to a huge potential for collecting and using data about the stuff in our cities (in this case, people’s possessions and property) and connecting and sharing it online to make cities a little better offline.