This is the neighborhood picnic of the digital age. With neighborhood social network, Nextdoor, communities can stay up-to-date with everything from crime, activities and even ask the neighborhood if they can borrow the proverbial cup of sugar.

Nextdoor announced on Tuesday that it just closed a new round of funding with existing and new funders: Benchmark Capital, DAG Ventures, Greylock Partners and Shasta Ventures, among others, to the tune of $18.6 million.

Nextdoor's CEO and Co-founder, Nirav Tolia, tells Mashable he plans to put the funding toward expanding their 32 person workforce and pushing Nextdoor out to new neighborhoods.

Already more than 3,600 neighborhoods in 48 states use Nextdoor, and about 22 new neighborhoods sign up for the service every day. This growth has allowed them to attract this most recent round of funding, Tolia says.

Here's how Nextdoor works: Login to find your neighborhood and sign up. Every user must verify their address. If your neighborhood's not there, you can be the person to start your neighborhood's social network through Nextdoor. You'll outline the boundaries and find the local school districts to include — yes, it takes some work, admits Tolia. But they want to avoid people signing up just to "kick the tires," so to speak. Invite nine of your neighbors to sign-up and have them confirm their addresses on your neighborhood within 21 days. Once that's done, your site is officially launched. If your neighbors don't sign up, or maybe you don't know enough of them, Nextdoor will alert you when someone else in your neighborhood successfully creates the site and then you can register.

So far, Nextdoor has been a popular forum for asking neighbors' advice on finding a good local electrician or plumber. Neighbors can also alert each other if any crime or suspicious characters have been spotted, he adds. In fact, Tolia says his 70-something-year-old parents use the site for neighborhood watch purposes.

"We believe there is an opportunity to build a private social network around location," he says. "There's a very big part of our lives that isn't covered by an existing social network."

Nextdoor launched nationally Oct. 2011. With this new funding, they plan to take it internationally by the end of 2012.

Each neighborhood's site is private, meaning no one else can access it, not Google images, nothing, he says. And it's not like Facebook or any other photo sharing social network, he adds.

Tolia says they slowly rolled-out the site to neighborhoods to make sure it would work in a variety of environments — from urban to suburban, affluent and low income — "we wanted to create something all neighborhoods would find useful." In the future, Nextdoor might get ad dollars from recommending local services on the site, but for members the site is free.

"We are not focused on monetization today, we are 100% focused on user adoption," Tolia says. "When we've experienced enough scale, we plan to do something that lets users derive more from the service."

Would you use Nextdoor? Tell us in the comments.

iStock photo, HultonArchive