I would second woocommerce. It's free, quick to setup, intuitive to work with, and actually scales decently. It also has a lot more features than you might expect for a free product. There's a huge ecosystem of support/plugins for it as well.
Even if you don't care about wordpress, you really can't beat the ease of setup and use of wordpress+woocommerce. Combine it with Stripe and a free plugin and you can be in business and accepting credit cards in hours.
The only thing I've found any quicker to setup is a hosted solution like magento GO, but with something like that, you have a monthly fee and are limited in what customizations you can make.