For the ultimate in backyard fun check out these Zip Line Kits that are easy to install and can keeps your Children out of trouble for hours during the Summer. I bought one of these last year and when I consider how cheap they are it is well worth it.
There are a few on the market to choose from with the prices ranging from $150 to $250 for most of the average kits which are perfectly good enough for the average home. Nearly everything you need (with the exception of safety kit) comes included so all you have to do is set it up.
To be honest this is not difficult and most people should have no trouble getting this up and running. The only slightly hard part is using a cable tension tool to get the cable nice and taught. This can be quite a workout, if you are unfit, but once that is done you are ready to go.