Many times, I've explained the library system to my children, and it never fails to blow my mind a little. I've expressed the amazing aspect of borrowing something you really want, using it and then returning it when you're done. For free.

Of course, you need to be able to print your name to get a library card. And the library is only free as long as the items are returned on time. And the library might even report you to a collections agency. But still, it's a pretty sweet system for those of us who want to consume more media than our budgets allow.

Recently, Little Free Libraries, which started in Wisconsin, have popped up all over the world. They are freestanding little book houses in front of private yards, businesses and not-for-profits that allow people to take a book and / or leave a book.

The website, littlefreelibraries.org, offers free plans to build one or the opportunity to buy an already-constructed one. Prices range from $250 to $600. The founders of the site will send a "take a book leave a book" sign for anyone's Little Free Library if they email a photo of it to them.

There are are hundreds, maybe thousands, of Little Free Libraries all over the world. Nobody is certain how many are in existence, but the site founders, Rick Brooks and Todd Bol, have made and sent out 650 signs already.

"This has spread like wildfire," says Brooks.

The goal is for 2,510 Little Free Libraries to appear around the world which is one more than the number of libraries built by philanthropist Andrew Carnegie.

The movement started in 2009 when Brooks and Bol, both from Wisconsin, met at a workshop at the University of Wisconsin-Madison and realized they had a lot in common. They decided to work on a project of some kind that combined their carpentry, entrepreneurial and international experience and came up with the Little Free Libraries concept.

Bol built the first one in the shape of a school house to honor his mother, a retired school teacher. Although there are plans on the website, there is no rules for building a Little Free Library. It's a concept people can take in any direction they want. The mission is simply to share books to promote literacy and build community in the process.

Madison is home to many Little Free Libraries, but dozens have popped up in Milwaukee during 2012.

Scott Gelzer and Pat Wyzbinski are the driving forces behind the influx of local Little Free Libraries. In 2008, the couple lost their then-24-year-old son, Brandon, who was a carpenter, and started an organization in his honor called Brandon's Tool Shed.

Every year, the organization takes on a community project that has a connection to one of Brandon's passions. In 2012, Brandon would have been 29, so Gelzer and Wyzbinski decided to organize the creation of 29 Little Free Libraries in Milwaukee.

"We really loved the pay-it-forward idea," says Gelzer.

In May, the couple celebrated Brandon's birthday with an open-to-the-public Little Free Library information and building session at the Historic Pritzlaff Building and about 200 people showed up. Bol led an information session and there were numerous carpenters and artists on site building and decorating.

Gelzer, who is the executive director of the Faye McBeath Foundation, says he is not certain how many libraries came out of the session, but he knows of at least 29, including one in front of the Downtown Montessori School in Bay View, another at The Grand Avenue Club Downtown and one in Jewell Park.

Little Free Libraries already existed at the Urban Ecology Centers as well as in South Milwaukee, the Washington Park / Washington Heights neighborhoods and more. The Walker's Point Center for the Arts plans to install one by the end of 2012.

Gelzer and Wyzbinski have a Little Free Library in front of their home, located in the Brady Street area. Gelzer says it has connected them to neighbors – many of whom have donated books – as well as instigated lots of conversations.

"For Halloween, we decorated our Little Free Library and gave away books instead of candy," says Gelzer.