Here's a hoot:
My mother has a couple touch lights in her bedroom. The kind where you just touch any metal part of the lamp and it turns on.
Well, her computer kept coming on on the other side of the house all by itself... and if it was left on with the monitor set to turn off, the monitor would come on at weird times for seemingly no reason. Then she made the connection: Any time one of the touch lamps was turned on or off, it would turn her computer or monitor on on the other side of the house.
She thought she had a ghost for months.