If your bus ride is a bit boring or you'd like to amuse yourself at the public library, then you can use Kevin Shay's UpSwing. It's a portable swing kit, complete with ropes, pulleys, and a canvas seat. Just sling it over a tree branch or overhead pipe, attach the components, and start swinging.
Swinging is fun. There's no need to miss the opportunity just because you're an adult.
-via David Thompson