I have an 802.11g PCI card (Trendware), new but open-box, that I will gladly trade for a 802.11b PCI card in good working condition.
There's nothing wrong with the card at all; however, it doesn't work in my old stupid Pentium II (motherboard issue), although it naturally works perfectly in my Mac (gets recognized as an AirPort card with no configuration at all). That's why I'd like to trade it.