Tienda is one of the newer pieces of software to integrate eCommerce into Joomla Content Management Systems. Because it was written specificially for Joomla, it blows Virtuemart out of the water. It integrates nicely with existing Joomla sites and uses your website's existing template, so it does not require extra work to match the design/feel of your site. You can read more from Dioscouri's page and download it for free.
However, because it is such a new software, there are some bugs and not much documentation. We now specialize in this type of site. You can view Tienda sites we have designed/developed in our portfolio
, read documentation in our documentation
section for other developers and view our list of our services
For end users using Tienda, we have set up a tutorial database for our existing clients that you can access on YellowWebMonkey (see Tienda Tutorials)