Yeah -- maybe you could call them and ask them to ship it without the adapter, since you definitely don't need it:
"To use an AirPort Card with certain iMac models requires the use of an AirPort Card Adapter kit. Any G3-based, slot-loading, AirPort Ready iMac requires this Adapter kit to install an AirPort Card....Other Apple products, such as iBook, Power Mac, and PowerBook as well as new G4-based iMacs, do not require this Adapter kit."
(from store.apple.com)
I have to disagree with SimX about Airport Base Stations 'cause I think they're way overpriced, like I've said before. Bottom line: if you have broadband (don't know about dial-up) the Base Station does much less at a lesser quality than other companies' products, which happen to be about half its price. And with Apple's built-in airport card slots and OS X, it is really very easy, even for a novice, to plug-n-play their way to wirelessness.
I can't understand why Apple won't bring the price down on the Base Station. Maybe they're trying to recuperate from the costs of building aiport card slots and antennas into all their (new) computers (unique to Apple, and very cool) and selling airport cards at competitive prices. Of course, they do have a $100 discount or something if you buy one with a new computer, I think. But that's still more than I would ever pay. I'll stick with my $150 Router + 4-port 10/100 Switch + Wireless Access Point + Web-based configuration.