Single Use Credit Card from Paypal

http://www.orbiscom.com/presscentre.php?presssection=news90
This is a pretty cool idea. It uses your Paypal account with a Plug-in from Paypal. Basically, it generates a 1-time use virtual credit card which is tied to your Paypal account and looks to a merchant like a Mastercard (even their billing shows Mastercard). The plugin, upon your approval, fills in the data for you on a merchant's site, including a 3-digit verification number. After the virtual credit card is used, it's no longer valid for subsequent purchases. So if the merchant got hacked and someone got the credit card number, it wouldn't do them any good. Paypal requires a credit card on file with them, which they charge when you use the virtual card. If you don't have enough on the credit card, it defaults to your checking account.

It also works on sites that don't take Paypal.

Here's the plug-in: https://www.paypal.com/us/cgi-bin/webscr?cmd=_vdc-plugin-intro