No drivers, even for an external (firewire) PC port on a G5.
If you get a 17" PB with the PC card slot, some third party wireless cards will work. There are also some USB solutions if you don't want to go AirPort. No non AirPort solutions allow for easy external antena connections.
AirPort is the easiest solution, though if you get more than one card, you can use some pretty cool wireless tools. For instance you could scan mutiple chanels at the same time, you could run mutiple networks at the same time, you could packet sniff and decode and connect to another network at the same time.
Supposedly some Lucent cards work and fit just like AirPort cards. That makes sence, as Lucent supposedly manufactures most of the AirPort cards parts.
Stick with AirPort. The antennas arent bad, and if your really gung ho and don't care about your warranty, drill out a bit of the battery case (the metallic lip) where the AirPort card resides, attach your own cable to your own antenna. AirShare.org has plans for the Pringles Can solution.