Arduino and robotics

Anyone in here using or used the open source Arduino microcontroller for robotics?
I’ve just finished my first LED light tutorial, and am onwards to the second tutorial. Also with a LED light. But this time with a button!

It’s really nice to program something and have it effectuated in reality. Even if it’s just a LED.
I’ve played with a nxt legomindstorm before, but this is in comparison much more hardcore and German.
Screws, wires, electricity… it has it all.