Only an original Apple Airport "B" card will work in the Ti's internally Airport slot. Having said that, you can use a 802.11g card (such as Sonnet's or certain Linksys / Buffalo) PCMCIA card which act just like a Apple Extreme card. This is in the external PCMCIA cardbus slot.
Again, no choice but PCMCIA card with the Ti's. (or original Apple card).. there was a link to a certain model Sony card which may work in the Ti's, but I would buy an Extreme (visit Accelerate your Mac if you really want a Sony / take a chance).