For a Halloween display - a ghost that could fly around my entire front yard - I built an inverted tripod machine with a 100-foot base leg. Took a couple of months to do, but the project is mostly complete. Details have been assembled on a website here:
Snotrag the Ghost, 2007
I'm using a P3-667 computer running EMC 2.2 Beta built from source. The system uses the HALUI elements to allow wireless USB joystick control in World coordinates. I've got a mechanical resonance issue that caused me to miss the Halloween deadline, but other than that, the system works really well.