The leading shopping cart software for Joomla is most definitely Virtuemart. The E-commerce component is highly flexible and integrates with Joomla seamlessly via the Joomla extension manager. Virtuemart is Open Source which makes this E-commerce system free to own. Joomla is also free open source software acting as the content management system for your website. With these two combined, you can have a beautiful content rich website that can transform into a beautiful and highly flexible online store.
Both Joomla and Virtuemart are PHP/MySQL driven applications and require some web design and server knowledge. Typically, more advanced users or web development professionals will be responsible for the initial setup of your Joomla Virtuemart website. Once everything is setup, then access is given to standard employees or clients to manage accounts, review invoices, track sales, update inventory, and more in a very easy to use interface. Because both Joomla and Virtuemart are free database driven software, you usually spend much less for the overall web site. While other e-commerce systems such as CRE Loaded require annual license fees, Joomla Virtuemart does not.