Algodoo

Phun computer working at 50Hz
It's turing-complete, so it can do any calculation given enough time and memory.
Programming language is fully functional and pretty easy.
Scene includes Fibonacci numbers sequence program as example. (pretty poor one because it fills whole memory with the numbers, instead of doing it in one place and only printing answers).

Memory and code can be extended to any length, just copy circles and change their restitution (they are enumerated by restitution, currently 1..16).
Main cpu code is in the middle box.

On the boxes around are some technical informations about working,
I used them while building it.

[EDIT]
I forgot to make jump instruction conditional, now the jump is not performed if current memory cell=0.

I also added means of starting and stopping/reseting computer. Now new programs can be inserted easily.