I'm trying to get a motor for using with the arduino, but am having difficulty. What I need is an electric motor for a turning a disc, running at about 3rpm even if a moderate amount of friction is applied to the disc, such as a hand being pressed against it. I'm not much good with these things so I don't know what I should be looking for in terms of torque and voltage.
you should be looking for a geared DC motor. And a rather heavy duty one. Or maybe a really big stepper motor.