pure alcohol is about 60cal / oz. (or 7cal / gram) IIRC.
so for something like absolut, whitch is essentially water + alcohol; 1oz = 0.4oz alcohol, = ~24cal / oz.
something like light flavored drinks (a la smirnoff ice, mikes lemonade, et al), or liqueurs (gran marnier, kahlua, etc etc) are a little different, because they have added flavor + sugar + etc.
edit: wtf. supertool's link is trying to prove me wrong. well wtf is the weight of ethanol? maybe the 60cal/oz is wrong.
edit2: a fvck it, i give up. i think ethanol is 0.78g/mL, which would be about 155cal/oz. why they gotta screw it up like that.