Sorry for the plug, everybody, but I know there are people around here who have been waiting for this. We’ve completed an early BETA version of USBSwiper for Magento.
The module works on 1.5.1+ and is developed as an extension of the built-in PayPal Payments Pro payment module in Magento. By enabling USBSwiper a Swipe field will be added to the credit card option during checkout in which you can swipe a credit card using a credit card reader and it will automatically fill out the CC details for you.
We’ll be adding more features to turn Magento in to a complete POS solution before long, but what we’ve got now works great.