I need to cool my garage. I do not have any ability to vent an ac unit as it is a townhouse. Is there any type of unit which I can purchase that does not need to be vented. Thank you.

You're going to have to find some way to get the heat out of the garage. There are "ductless" systems that only a 3" diameter hole for a refrigerant line - see:

Mitsubishi Electric - HVAC Advanced Products Division: Products: Homeowner

This type of system that Ebains mentioned is a good way to go but you will still have to have a condensing unit out side somewhere, they also make a portable self contained a/c that exhausts the condenser air like a clothes dryer but it is a 6" round that has to go through a wall or window,