Windows only: Getting your child to sit still for any prolonged period of time is difficult, even with most computer games. SoupToys, however, is a set of desktop physics-based toys that will keep your child — and probably you — endlessly entertained.
The sheer volume of different virtual desktop toys in SoupToys is mind blowing. The free, downloadable "toy box" comes with over 100 items inside, each with its own properties that interact with other toys just like they would in the real world — you can pick up toy cars with magnets, roll balls down ramps and into basketball hoops, or just drag a pirate ship around your desktop to hear it say "Arrr". And, if those 100 toys somehow manage to get boring, you can download (and upload) pre-made "playsets" to jog your child's imagination and use the toys in different ways.
The other nice plus is that, despite it using your desktop as a playground, you can change it to something different if you don't want your child accidentally messing with your folders. And, when it gets too messy, you can clean up the entire playset with the click of a button and start all over. Honestly, this thing is addictive. I'd recommend it as a nice stress reliever for adults, too, if it didn't also have the potential to be the biggest productivity killer of all time.
SoupToys is a free download, Windows only.