Interesting Article
Here's one I'd never heard of.
4. Keystroke catchers. These small devices are attached to the cable that connects your keyboard to your computer and can be bought online for a little over $100. The "catcher" resembles a standard connector, but contains a memory chip that records everything you type. It's typically used in public places where computers are available, such as libraries, Internet cafes and college computer labs. To protect yourself when using a public computer, never shop online, check your bank account, pay bills or enter your credit-card information.