Urban renewal project

Content Love informs us that LED + magnet + battery = Throwie.

Now, find a building or structure that will attract the magnets, form a crew, wait until night, and get some throwies up. If you do it around a crowd of people, they will probably try to get into the act. It can quickly dissend into chaotic fun. Give a hand-full of throwies to a stranger and let them get up too. Remember, Throwies are only a temporary alteration of your local environment. Depending on the color, Throwies can last upto two weeks, but you arent going to cause any permanent damage, so most property owners wont mind. And The NYPD loves throwies!

Throwies are described on the Instructables website, which also includes countless other cool DIY projects, like an iron pipe bed, a treehouse, a zoetrope, and pesto. Mmmm ... pesto.