Following are few of best WordPress eCommerce plugins. Picking an e-commerce solution depends on how much money you are wanting to spend (if any), what you need your e-commerce solution to be doing and how much knowledge you have in relation to running, developing, and customizing e-stores.
Ecwid is a free plugin for WordPress. It is a full shopping cart/e-commerce system that is extremely easy to install and even easier to maintain. It’s also customizable so you can have it looking however you like. See their showcase gallery that features live sites that use this WordPress plugin.
eShop is an accessible shopping cart plugin for WordPress. It is packed with various features, including basic statistics, sales data, various payment options, various methods to list products, basic stock control and various discount options. Most importantly, it can be linked with multiple merchant gateways including Authorize.net, Paypal, Payson, eProcessingNetwork, Webtopay, iDEAL and Cash/Cheque!
Shopp is an e-commerce plugin that adds a feature-rich online store to your WordPress-powered website or blog. Get your store up and running in minutes. Then, take it to the next level with the flexibility of Shopp’s customization tools that allow production studios and power users to tailor every aspect of the shopping experience.
PayPal Payment Terminal WordPress: http://codecanyon.net/item/paypal-payment-terminal-wordpress/166082
With its super easy installation, PayPal Payment Terminal WordPress allows you to start accepting paypal payments on your wordpresssite. You can display it as a widget or on any page/post, view and sort all transactions and send out automatic notifications to your customers and yourself.
uPricing – Pricing Table for WordPress: http://codecanyon.net/item/upricing-pricing-table-for-wordpress/145538
uPricing is a pricing table for WordPress. It is a standalone plugin that allows you to create a pricing table to list your products in. Perfect for comparing products across their features and price.
The WP e-Commerce Plugin is offered under GetShopped and is a shop owner’s dream. It offers a fully integrated shopping cart application suitable for selling your digital and tangible products, services, and or fees online. It can be integrated with Google Checkout, DPS / Paystation, Paypal and offers an audio player module for selling mp3 files and digital downloads. Its functionality can be extended by using add-on plugins.
PHPurchase allows you to sell digital and physical products, collect recurring payments for subscriptions, memberships, and payment plans. You can even build a complete membership site with plugin and set up coupon codes for promotions.
Quick Shop: http://wordpress.org/extend/plugins/quick-shop/
Quick Shop supports any WordPress that has the sidebar widgets installed. It adds a SideBar widget that shows the user what they currently have in the cart and allows them to remove the items, not to mention a TinyMCE button to easily allow you to add products to your posts/pages.
If you already know how to use WordPress, using an WordPress e-commerce plugin is definitely something to strongly consider.