DD and all her friends play in the street here. We live at the circle end of a cul-de-sac, so the kids are pretty safe. Also, they only play in the circle if parents are out supervising them (honestly, the grown-ups usually congregate in the street, too). They are all trained to go to their driveways when they see a car.
When DD is allowed to play without my supervision, she is allowed in the back yard and surrounding greenspace. She carries a walkie-talkie and checks in periodically. She and her little friends go "exploring" with their snacks and backpacks- they play in the trees, look at the tadpoles in the creek, pretend to camp out, all those fun things that can't be done with old Mom watching them from the porch. I started allowing her to do this recently, when we got the walkie-talkies.