This is a short list of things that I have found online that I think are interesting.

Context Free Art is a computer programming language that allows the user to create interesting patterns using math. At first it is a bit daunting, but pretty easy once you get used to it.
http://contextfreeart.org/

Scratch is another computer programming language that allows the user to create video games of surprising simplicity or complexity.
http://scratch.mit.edu/

Sketchup is another great free product from Google. It is a 3d rendering and drafting program. I have been using it to design rooms in my house. I have seen people use it to draw 3D representations of machines with incredible detail. This is also the place to create a 3d likeness of your house that you can put into Google Earth.
http://sketchup.google.com/