Today I am recommending a new Smartphone App for accepting credit cards called Square -- http://squareup.com -- I think it's a perfect addition for any on-the-go business! This App was created by Twitter inventor Jack Dorsey. Read more history behind the new App.
Basically, you download the free App to your Smartphone and then complete the registration process online. It took less than 10 minutes to get set up, there are no monthly fees, and the charge is about 3% more or less depending on if the credit card is manually keyed in or read with the free swiper attachment. Once the credit card is read, the customer signs the phone and then receives an emailed receipt. Note that you definitely need WiFi to run the reader!! An optional way to compute sales tax would be helpful, but overall the Square format is clear, easy and very fun to use!