As some of you know, I eventually plan on returning to school to become a mechanical engineer. While looking up different machines and engines, I came across a number of LEGO machines (many using their more advanced sets like NXT, which include motors, a computer of sorts and other stuff).

This first one is a steam powered piston engine (except a pump is used to blow air into the intake to act as the steam, but it's the same operation):

This one was really cool. It's basically a printer that builds designs created in a LEGO CAD program. It's slow, but it's pretty cool:

Here's a machine that lets you select a beer, it pops the cap, and apparently cools it:

And here is one of the coolest ones I could find. It solves Rubik's Cubes in a matter of seconds using a phone and an app: