Tomato Firmware: Usb Hard Drive as Network Attached Storage (NAS)
We've done it with DD-WRT already, but if you're running tomato and want a network drive, its quite simple, follow along with this video and see for yourself.
Ensure your router has a large enough flash to store whatever usb build you decide to use, and verify you have the proper mipsr number.
failure to do either of those steps could brick your router. the selection is covered for the belkin routers in the flashing video.
You'll be sharing files in notime.