You're a few weeks late with that question.... I got a flat a while weeks back, so I could have weighed a wheel and tire seperately while it was apart.
Well, it could be together. I just want a total for comparison when choosing new wheels. But that would have been convenient, since you had one off the car anyhow.
If you are looking for a lightweight aftermarket wheel, the OZ Superleggera is a good place to start. Not sure if that is the look you're going for, but they are pretty light. In fact, I believe "Superleggera" means "super light" in Italian.
All I know is that they are very heavy. When I rotated my wheels a week ago (on my 09 GT), I remember thinking that I never felt car tires this heavy. They are definately not on the light side for alloy wheels.
Got a bathroom scale? pull a wheel and see... i'll tell you right now though... The tires are heavier than the wheels... my guess is the avarage tire is about 30lbs... I bet the wheel alone is about 20lbs.. it would be nice to know for sure though..