Ran across an interesting website. www.feefighters.com They basically are a site that allows you to have credit card processors 'bid' for your business. Interesting concept.
They also have a blog of some great articles, with information like making sure that you are getting interchange plus pricing rather than arbitrary markups on your transactions.
There is also a useful tool for comparing Square pricing to a more typical processor. Tool is a bit buried but the link is http://FeeFighters.com/square-calculator since the Square seems to be revolutionizing the way credit cards are charged.
Got my Square swiper this week. If you have an Ipad you can load a photo of your art piece with description and pricing which will flow through to creating the invoice and then the email that goes to the customer.
One other thing I learned is that we all seem to focus on the lowest rate for a fully qualified card yet nearly 80% of transactions today are at the 'mid rate' since they are done with affinity cards. And that rate is almost always higher than the the lowest rate.