The following list doesn’t attempt to be perfect neither showcase the best CMS. It is merely a review of the most popular eCommerce specific CMS out there, both open source and paid ones. In the end, there’s a list of eCommerce plugins for some generic CMS like WordPress, Drupal or Plone.
Free eCommerce CMS
Paid eCommerce CMS
http://virtuemart.net/ (also available for Mambo)
WP e-Commerce is a free plugin but if your store grows and you need more special features you can buy them as modules at a low price. You can see various screenshots of the admin interface at the Dan Milward Flickr account, it really has a lot of options for an entire post.
This is a theme as it name implies. Of course, there has to be some plugins in there but the installation is transparent to the user. You can use the new post section to add a new product with several custom metaboxes to enter information about your product. Market Theme doesn’t have a free option but the standard license is only $ 55 USD, and you can customize it and have access to unlimited upgrades.
Another theme to turn your blog into a full featured store. It is also only available for purchase. After you pay, they take care of setting up the site for you.