"Hi Mike.
I was able to get a linksys wireless-G (802.11g) card to work on my Lombard powerbook! I knew the Airport chipset was a Broadcom chipset, in fact, the same chipset that linksys uses in their wireless-G products.

Today I got my Airport Extreme base station, but I only have a lombard laptop, which doesn't support Airport Extreme directly. The CD that came with the airport extreme contains the /System/Library/Extensions/AppleAirport2.kext, which is the driver for the wireless card in the new Airport Extreme enabled desktops and laptops.

The new apple cards are on a PCI bus (with some weird connector I'm sure), but a PCI bus is a PCI bus. CardBus cards are also PCI cards, so it seems that with the same chipset/bus, the apple drivers should work just fine with the Linksys WPC54G. In fact, they do if you play some tricks on Mac OSX.

Here are the steps to make this work:
First, you need to find out the PCI name of your linksys card. To do this, you need the terminal:

ioreg -l | less > ~/devices.txt

This will create a file called devices.txt in your home directory. Open this with your favorite editor and search for "Broadcom". This is the linksys PC card you put in your PC. If you look closely at the following lines, you will see something that says:

"compatible" = <"pci1737,4320", "pci14e4,4320", "pciclass,028000">

Now copy that first pci1737,4320 (it could be different on your machine, i'm not a PCI expert...is this number static for the card?). Now:

cd /System/Library/Extensions/AppleAirport2.kext/Contents

edit the file Info.plist
Change "Broadcom PCI" to "Broadcom 802.11b CardBus" then change the <string>pci....</string>
by pasting in the pci stuff you copied from the ioreg output.

Now load the kernel module by doing a
kextload /System/Library/Extensions/AppleAirport2.kext

Now run the Apple airport admin utility to configure your airport base station! Internet Connect may work at this point as well.

This is a bit rushed, and I'm sure somebody will put this together into a nicer package or applescript (I don't have the time), but the point is, you can add airport extreme to your older powerbook for $70! Thanks to Nick Sayer, who helped me get this going....
Good luck!
Charles Archer"