Some months ago I had been looking into options for Jenny and David who wanted to open up a little 2nd hand store which sells commissioned stuff and use their Mac for it all and one of the best options I found was MacPOSX :
MacPOSX enables you to use a Macintosh at the point-of-sale in your business. It could be your laptop at a trade show, a PowerMac in the back-office, an iMac at home or at the checkout counter of your store.

Flickr
Stumble Upon
FriendFeed
Twitter
Delicious
YouTube
LinkedIn
Facebook