I have a trampoline. It's down near the washing line, so I put the kids on it while I'm hanging out washing so I know where they are and that they're out of trouble. They love it. I try to get them on it for a while in the morning to use some excess energy so they can concentrate to sit down and listen to a story afterwards. It's great exercise and they sleep better.
I loved my trampoline as a kid, but I'm glad the new ones are a bit safer than the one we used to have (no net and dodgy padding so you could fall on the edge or the springs or get bounced right off).