Describe the suggestion
When applied with a redstone pulse, turntables will rotate one notch around clockwise, direction can be inverted with a redstone torch.

Applications of the suggestion
Can be used for run-around loops with Vorlord's excellent automation code.

In addition to the pulse, I propose that a continuous redstone signal would allow the table to rotate until the signal was turned off. This would allow a 180-turn (which can be pesky due to the wrench operation) to be done easily with a timer circuit or player with a lever in one spot.