PaulSV
Treadmill motors generally are 5000 rpm DC motors with controllers. Turning them at 60 RPM would give very little torque, unless there is significant gear reduction. Treadmills have such gear reduction, but not built in to the motor, and what is there may not be adaptable for the OP's purpose. The motor and gearing used for the incline feature of a treadmill may be more suitable.

A gearmotor will have the gearing built in, and may be easier to adapt to the OP's intended use. You can get a lot of different gear motors relatively cheaply from Surplus Center, here:

http://www.surpluscenter.com/electric.asp?catname=electric

Another cheap possibility would be the motor and built-in gears of an old KitchenAide stand mixer. I am not sure, though, if they are continuous duty motors, suitable for running a few hours at a time.