Sun Labs Lively Kernel
You need to download safari browser(now available for Windows too) to explore this. Then click the "enter lively kernel" tab at the above site.
It's fairly amazing but needs more development. Not all of the commands work on my keyboard, by the look of it you need a Mac
Dan Ingalls explains The Lively Kernel on this You Tube presentation:
It's a long video but if you watch the first 10 minutes you'll get the idea.
You can move objects around on the screen by dragging, copy objects, edit objects, compose objects (drop one object on top of another and they stick together), scale objects, rotate objects, resize, write scripts, objects can inherit behaviour from other objects, etc.
Fun is one goal of this project