Although It's not a PCI card, I've had good luck with the ZONET ZEW2508 802.11G USB ADAPTER. I purchased a few of these USB adapters to help friends and family get their PCLOS systems online And there's the added bonus of easily moving this adapter from PC to PC, you can use it on notebooks too. They're available from Lin PC HERE
(second item on this page). One note - you must be running the latest kernel, in my case that's 126.96.36.199-pclos1.bfs, earlier kernels don't seem to support the chipset used in this adapter.