Well you could write your own firmware? and use it as a custom network controller....or scrap it for parts ^^
Anything inbetween those two would be really tricky...wifi (802.11a/b/g) has many many layers to it, most of which will be embedded within the IC's inside the router. Unfortunately its not just a case of having a generic '2.4Ghz transciever'. Spread spectrum, encryption, convolutional encoding/decoding are just some of the goodies inside any wifi capable device - cards, PCI adapters, and routers. etc..
The best idea I can come up with is a mobile wifi LAN. As in, try and reduce its power consuption, rehouse it inside something, and use a SMPS powered by batteries. Or even better, rig it up to a car so its a 'mobile WLAN'!!
As for getting into the guts of it and using it for something completely different?....who knows. What did you have in mind?
Blueteeth