nopCommerce is the popular open-source eCommerce solution. It provides fully customizable, stable & highly usable shopping cart. And it is totally free.
You can also download it's source code from here.
You can see the demo from here.
There is an ebook available for beginners here.
Lots of video tutorials are available on the internet, just google it. And almost all major web hosting providers also supports it.
Finally conclusion: It is good & perhaps the best free eCommerce solution available in the market. Go for it.