WordPress being a popular blogging platform and content management system, it can also be used for powering e-commerce websites.

The flexibility of WordPress has always been its strong point. You can find the Reasons to use Wordpress as the platform for your site.
Although the primary purpose of WordPress is not e-commerce, it provides e-Commerce platform with a focus on aesthetics, web standards and usability. It is both free and premium.
There are number of plugins and themes available that provides easy mechanism to create your online store. Here I am going to list top plugins according ti their use:
Plugins:
1. Wordpress eShop

eShop is a free plugin that also has a lot of features and options for setting up an e-commerce site with WordPress.
2. Instinct WordPress e-Commerce Plugin

An extremely popular plugin that offers a lot of options for setting up an online store with WordPress. WP e-Commerce integrates with PayPal, Google Checkout, Authorize.net and more. Designers will have the flexibility to tweak and customize the appearance as well.
3. Shopp

Another popular e-commerce plugin. The cost is $55 for a single-site license or $299 for a developer’s license. The plugin includes a lot of features, including several payment options and flexible shipping calculations.
4. Quick Shop

Quick Shop is a free plugin that users sidebar widgets to create a simple shopping cart. You can place tags in your post that will generate a form to add products to the cart.
5. YAK for WordPress

YAK is a free plugin that creates a simple shopping cart that associates products with posts.

You missed WP-e-commerce plugin. IMHO it is one of the best plugin for driving eshop. Anyways a great collection.
Oh… Thanks very much…
WP e-Commerce : http://wordpress.org/extend/plugins/wp-e-commerce/