Look at Cradlepoint's routers.

http://www.cradlepoint.com/

For a discussion of many of the products out there, look at:

http://www.evdoforums.com/

You can't use an Airport directly with a USB modem, you'd need some intermediary device. Linksys makes a USB modem router, but I like Cradlepoint far better. They have several devices that travel well (e.g. are small and multifaceted). I travel with the PHS-300.