Depends on what you want to connect. One printer only. And there is a very limited list of other devices that work through an AirPort express. If you had done a search for "airport usb hub" on Apple's Support Site you would have had a full answer already.
Nope, the Express doesn't support hubs. Only printers, some remote control devices and I believe you can charge a shuffle or an iPod through the USB port, but that's it.