DiscoRunner comes with a library of close to a thousand classic programs to play, edit and muck around with -- a good way to learn introductory programming concepts while exploring early computing history with programs like Oregon Trail and Steve Wozniak's original Breakout.
These are rendered in OpenGL 3D so you can move the camera around and give a modern feel to these games from the 70s and 80s.
There are also hundreds of bundled text-adventures to get lost in too -- or write your own!
DiscoRunner