This could lead to a very useful idea that I think a lot of people would go for. I use a USB card swipe reader I got for free for taking credit cards (looks exactly like the one in iaxai's post). I use a web-based credit card processing company, so I tell their website to get ready to accept data from the USB, swipe the card, and bingo ... the card data is ready to be submitted securely. So it's just a script running on a webpage. I've used this on several computers and never needed to do anything special to set up the USB card swiper.
Seems like somebody should be able to make a script that runs on a web page so you can have a little browser open that waits for a card swipe to occur. The beauty of this is that, once the little web page is available for download, anybody with the cheapo/free USB card reader would be up-and-running as long as the computer they hooked it up to could run a browser that could run the script.
A think client hooked up with USB card reader could have a lot of good applications, both commercial and plain old fun.