I'd recommend prestashop. http://www.prestashop.com/ it's very easy to use and install for the non coder. i've used only a few of these e-shop apps, and this one was quite nice. extensible with lots of addons for nearly everything. :good:
I have used Prestashop, Opencart, WooCommerce and Virtuemart but nothing beats Magento. Though it gave me headache during initial installation, it is a great E-Commerce CMS. If you are good...and I mean really good in PHP, you can extend it the way you want. But if you are not, please go for Prestashop. It is quite comprehensive too and user friendly.
I'll be honest; when I looked into shops when I tried to start an e-commerce business, they all seemed roughly the same. I ended up finding a comparison list of them, checking out each site, and it really just came down to a couple minor features that one had over the other or what have you. In the end, I think I chose OS commerce, only because it had more template options than the others at the time. Magento seems to be the new gold standard though
Yes, PrestaShop is a not bad choice and its template is responsive. Of course many free e-commerce software only basic requirements and charge you if you wants more. Remember nothing is free.
Besides of Presta, there are Loaded commerce, Abante Cart &TomatoCart.