While I was in San Francisco, I was introduced to the Square Card Reader. The reader gets low app ratings on iTunes because the readers are backordered and hard to attain, with waiting times of 3-6 months, but the reader is free and the rates are low for occasional credit card swipers. I think once you've requested your Square Card Reader you have to pretend that it doesn't exist until you actually get yours to save on the frustration of not getting it right away. Imagine what this would do for your yard sale!
Willo in the video below has graciously offered to send me a Square Card Reader to try out, so hopefully I will get it before the Printer's Fair this weekend and I'll let you know how it works out!