[david-given]

...and if you're interested in doing more than playing games, there's assorted abusive things you can do with the Z-Machine.

Here's an ANS Forth: https://code.google.com/p/zmforth/

Here's Andrew Plotkin's infamous Lisp tutorial (complete with Lisp implementation for the Z-machine): http://www.eblong.com/zarf/zweb/lists/

I ported a C compiler to it, poorly, and made it play chess: http://cowlark.com/vbcc-z-compiler/

And, of course, you can design processors to run it on real hardware: https://github.com/charcole/Z3

[sehugg]

And Graham Nelson's Inform 7 compiles to two different editions of the Z-machine: http://inform7.com/