I have had one of these for several years:
DIGITAL 75 LB SHIPPING POSTAL SCALE POSTAGE LB SCALES W - eBay (item 350148935511 end time Feb-03-09 08:23:52 PST)
And it has been reliable and accurate (as far as I know, as nothing's been returned to me).
I haven't heard anything about a USB one, they look like they are about $10 more, pretty neat if it can directly input the weight for you.
60# "ULTRASHIP U2" USB DIGITAL SHIPPING POSTAL SCALE z - eBay (item 250351880586 end time Jan-06-09 15:38:57 PST)