mac os x as it stands doesn't allow usb printer sharing. however, most of us think that the next release, version 10.2, will have usb printer sharing.
a program called DAVE (thursby.com) does this in os x now, among other things it does.
you could get a print-server thing, which might interface with your usb printer and let it connect straight to the network, allowing your os x machine(s) to print that way. I believe HP makes one such device.