I've had this image of the Cherry-Picker Operation Interface in my phone for a while. Although graphically it's a bit inelegant (arrows too large, too contrasted from the white outline) it definitely provides a clear illustration of how to operate each distinct element of the device.
I appreciated the simple premise that you overlay the functionality against the subject itself. The Table of Contents page from Allure provides this handy little "widget," which operates on a similar principle. And the most successful web interfaces do this as well.