This article making the rounds is an example of an innovation that looks promising:
State of the Art
A Simple Swipe on a Phone, and You’re Paid
By DAVID POGUE
Published: September 29, 2010
Of course, other places, cell phone users have found it commonplace to pay via their cellphones. This service offers another option for getting paid for non-store purchases. Making use of the computer that is your cellphone, the Square up system allows users to exchange funds and track purchases/sales. It will be interesting to watch how these services pan out.
So let’s say someone from Craigslist comes over to buy your old junk. You snap the Square reader into your phone or tablet. You tap in the amount of the purchase; it could be $1 for a yo-yo, $25 for a box of old records or $12,000 for a used car (there’s no maximum amount). You type a description if you like, and maybe even take a photo of what you’re selling.
You input the payer's card information and bob's your uncle.