Here's another good resource.
http://www.tirerack.com
Plug in the make, year, and model of your car, then go to the wheels section.
They'll show you all the wheels they have that will fit your car in various sizes and they'll show the offsets for them, and what size tires you need for them. They also have a feature where you can see how the wheels would look on your car.
Between that and the thread the Bigbird posted you'll have a whole lotta info.
Most people on the forum seem to go with 17" or 18" wheels. Some go smaller (I'm running a 16" BBS wheel on my '95). A few go larger. It all depends on the look you're going for, how much you want to spend, how you want the car to ride, etc.
Be aware though that if you don't lower the car, installing bigger wheels tends to give the car a bit of a 4X4 appearance. If you don't intend to lower your car and you don't want to get the 4x4 look, then I'd consider 17" or smaller (of course, this too is a matter of personal taste).
Also be aware that if you get aftermarket wheels, you'll likely need hub centric centering rings to fit the wheel properly to your hubs.