If you have a Mac and you're talking about the wireless card to go inside the Mac, then either an AirPort card (older Macs) or an AirPort Extreme card (modern Macs) is your best and almost exclusive option. If you're talking about the AirPort Extreme or Express base stations, then no, you should be able to use any 802.11B or 802.11G wireless router.
My son's iMac is pretty far away from his mom's wireless router so I bought him a MacWireless High Power 11g Base Station. The iMac thinks it's on a wired network. You just run a patch cable from the access point to the Mac. Works great
Thanks all. Situation I should've explained. I have a RangeMax240 that I use for the networking option and my Dell laptop (business laptop unfortunately), but I have macs around the house along with my PowerBook. I wanted something different for my PowerBook that would pick up a faster signal than Airport Extreme. Thanks for the help!