Nope, there are only PC Cards and there is no way to get them to work with a non-PC Card computer, such as an iBook.
Your only choice is to use an Internet-enabled digital cell phone that is compatible with OS X using either a USB connection or a Bluetooth connection. Depending on your cell phone provider's cell phone internet access the connection speed can be fairly decent. And if you equip your iBook with Bluetooth using a USB adapter and get a cell phone with BT you can make the connection wirelessly between the two devices. Thus you could put the phone in your pocket and walk around with your iBook and maintain connectivity.