This is how i got my D-Link DWL-G520 (Rev B ) working as airport extreme in snow leopard 10.6.2

(This may work for other cards that use the Atheros Communications Inc. AR5212 / AR5213 chip, just add your device id to IO80211Family.kext/Contents/PlugIns/AirPortAtheros.kext/Info.plist)



Download IO80211Family.kext here and unzip it to your desktop.
Install the IO80211Family.kext with kext helper.
Repair disk permisions with disk utility.
Reboot.
Go to system preferences and add new network device, should now show airport.

Et voila