Indie Craft Shows has an article about getting started with credit cards.
I know that for now, I’m still with Paypal using Paypal Pro. I’ve adopted the virtual terminal to accept credit cards over the phone, fax, or snail mail which as been a God send. I don’t do enough open air shows to warrant a device that allows a business gal to take cc on site -but I think they exist.
Meanwhile, if your a CostCo member, it seems that they’ve got a pretty competitive rate for small biz.