Before you beat on it with anything else, can you post a picture, or give us a better description? Does the shaft extend beyond the pulley? What kind of material is the pulley--cast iron, zinc/zamak/pot metal, aluminum, sheet metal, something else? Is there much space between the pulley and the motor? All of these may affect how you want to procede.
If the shaft extends beyond the pulley, your first task is to clean it thoroughly, and file off any mushrooming at the end of the shaft or any dings on the shaft. As others have noted, remove all set (grub) screws and check for two of them in the same hole. Dose liberally with penetrating oil--not WD-40, it's cr*p. Put some down the screw hole(s) as well as at the hub. Walk away for a few hours or a day to give it a chance to get in.
If your pulley is cast iron, you can try with a 3 arm gear puller (which I assume Stew posted, but I can't see it right now). If it's anything else, I'd get a piece of plywood (half inch or thicker, whatever will fit between the pulley and motor), cut a disk a little bigger than the pulley, and put a slot in it to fit over the motor shaft. Then put the disk behind the pulley and try with the puller, hooking onto the plywood to distribute the force. Failing this, warm up the hub with a propane torch, keeping the flame away from the motor. (I've never needed to use heat on motors, though.)
Kirk