The only current Pocket PCs that can use PC Cards are the iPAQ which accept sleeves (3900 series, 5450, 555x). You'd also need to buy the PC Card sleeve along with the iPAQ and make sure the PC Card you're using has Pocket PC drivers (not many do).
In the end, it's usually easier and more cost-effective to buy a CF WiFi card instead.
-------------------- Lisa Gade Editor in Chief, MobileTechReview