Magento
It is hard to refute the popularity of this eCommerce platform especially when you consider the fact that there are more than 200,000 businesses online that rely on this platform in order to be able to gain some ground in the industry. It thrives on the fact that it is more than just powerful. It is flexible and cost effective to the users.
OsComerce
Perhaps one of the best things about this one is the fact that it is open source. OsCommerce basically stands for open source commerce, and as a store management program there are thousands of websites that depend on it. There are experts behind the scenes that make sure that the hundreds of thousands of businesses that are leveraged on OsCommerce are able to thrive every other day.
OpenCart
OpenCart on the other hand offers online businesses the chance to conduct their activities smoothly and economically. This is a very good thing for those users who are conversant with the operations of protocols like MySQL and PHP because it can aptly run on servers that are optimized through this manner. It is also available as a free software as specified in the general public license relating to the GNU.
Zen Cart
The biggest difference between Zen Cart and the other eCommerce platforms is that it is run as a store management system. It may share a thing or two that is similar with OsCommerce, but perhaps this is only because of the fact that they were designed as one project until they separated back in 2003. Basically Zen Cart allows web managers to interact on a higher level with the user demands through the customer management and promotion tools available.
WordPress
It is rather inconceivable for you to mention anything about eCommerce platforms without passing through WordPress (WP). This has possibly been the revelation for so many website users today. It brings forth a sense of functionality that was not possible with the likes of Google's Blogger, and since then there are a lot of people who have been able to make the best use out of it so far.
Conclusion
One of the best things about using these platforms is the fact that most of them are easier to use even for those who do not have an idea about how to build an eCommerce website, especially those who do not have the technical capability to do so. Therefore if you want to get your website online, it is time you considered some of these platforms.