Extensive G3 and Pre-G3 Wireless Configuration Advice
Derek Miller wrote a long and exhaustive article on adding wireless access to older Mac laptops. He has a PowerBook 1400, but his advice applies to the 1400, 2400, 3400, and G3 series that lacked AirPort card slots but had PC Card slots. He points out that even some older machines might work with old Orinoco (WaveLAN/Agere) cards.
Anyway seeking to add wireless support to their older laptop should certainly read Derek's article first!