wrong information much.AirPort Express USB ports are only for printers. You cannot hook an external drive into there. Using an AirPort Extreme + hard drive is possible with some tweaking in Terminal to allow Time Machine to write to a usually unsupported drive.
YES, you can hook up an external drive to Airport Extreme and use it for Time machine backups. This wasn't possible in the past but an Airport firmware update began to allow this.
Get yourself an AEBS and an external drive are u're in Biz Ness.
What, pray tell, was wrong about my first post? I wrote that the USB port on an EXPRESS doesn't allow for the AirPort disk functionality. I did point out that the EXTREME does...so where am I wrong?