What is the best web store tool?

I’ve never actually used it, but I’ve heard lots about Zen Cart. It’s free and open source, as well.

BigCartel looks pretty good.

I would suggest a hosted solution if you are going for usability. For example, both Yahoo and Volusion Commerce offer nice, easy-to-use plug and play shopping cart platforms. They are scalable and easy to learn. Using open source carts is cheap, but more complicated. Now, if you already have a store, you may be asking something else. Are you looking for a store solution, or a solution for your store?

http://ecrater.com is not bad

just be sure to understand your needs. If you are trying to build a large sustainable eBusiness, do not skimp out on the initial solution.

Magento. It’s open source, completely free, and has more features than a lot of pay carts. Magentocommerce.com