The Foundation have just blogged this nice little project from Instructables user DevinL9.
He’s taken a Raspberry Pi, hooked it up to a servo and then used the servo to control the position of a small fan with a small webcam mounted on top. The webcam provides a video feed to the Pi which is programmed with OpenCV to detect a face and track it. The servo then turns so that the fan always points towards you. For those long, summer months it could be just the job! You can read the Instructable here.