Here's a cool gadget you'll be seeing around yours truly and maybe some of your other favorite authors. It's called the Square and it allows you to turn your iPhone into a credit card swiping machine. I recently picked one up to facilitate sales at my personal appearances.
Easy peasy. You download an app and they send you the peripheral device for FREE.
Sure, they take a small cut of the transaction but I think it's totally worth it considering I'm reaching people who might not have made a cash only purchase. One more barrier kicked to the curb by the use of technology, and a major win for personal sized businesses.