I know that new desktops don't come with Airport cards. I believe all powerbooks do, and maybe ibooks. You;re best bet is to go to the apple store site or wait till someone not as retarded as myself responds.
All new Macs right now are AirPort Extreme-capable.
Recent computers that aren't AirPort Extreme-ready are the G3 iBooks, and any eMac with a processor speed below 1 GHz, and TiBooks. They all use AirPort.