People often ask about which Wifi card to buy to use with Linux, and in the past this was a difficult question to answer. When you're talking about a card to use on a PDA the available selection is even smaller.
However, on a whim I recently purchased a SparkLAN WCFM-100 which is an 802.11b/g CompactFlash card to try it out. Linux compatibility was listed in its product documentation, which is a good start.
It didn't quite work out of the box, however all I needed to do was enable building the libertas and libertas_cs modules in the kernel defconfig in OE, rebuild it, copy the modules over to my Zaurus, extract the firmware (instructions here) and copy that over to the Z, load the modules, and it worked. So I would definitely recommend this product to anyone wanting a wifi card for their Linux-based PDA. When I get some time I will try do document the procedure properly and/or submit some patches to make it easier to get working in Angstrom.