Todd Esposito

SimpleSeller adds a new post type to a WP blog, which represents a sellable 
item. Each author (“seller”) enters their own payment credentials, and 
posts are linked to that seller’s payment gateway with a simple buy-now type 
button. A separate capabilities set allows the blog owner to differentiate 
between those allowed to post blog entries and those allowed to sell items.
<h3>Updating</h3>
<ol>
<li>Download <code>simpleseller-latest.zip</code></li>
<li>Back up your database and previous version of Simple Seller</li>
<li>Unzip Simple Seller into your WordPress plugins directory</li>
</ol>
<h3>Setup</h3>
<ol>
<li>On the Admin page, select “Simple Seller” under Settings.</li>
<li>Choose a “slug” for all items for sale. SimpleSeller will create a page under that slug.</li>
<li>Edit the newly created seller page, adding whatever content makes sense. Publish the page.</li>
<li>(Optional) Create accounts for your “sellers”, or add the “seller” capabilities to existing accounts. We recommend using the [Capabilities Manager (capsman) plugin] (http://alkivia.org/wordpress/capsman) to manage this.</li>
<li>Enter your PayPal credentials on your Profile page. Each seller must do this.</li>
</ol>

Simple Seller

Adds a very simple sell-a-product capability to a WP blog.

Rolf Allard van Hagen

zackdesign

AliasIO

Note: This plugin requires PHP 5
Quick Shop supports any WordPress that has the Sidebar Widgets installed, really. 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.
Also, you will need to make your own CSS for this. I’ve included enough classes/ids for you.
Features:
<ul>
<li>
Inventory listing tied in to TinyMCE
</li>
<li>
Integrates automatically with CFormsII (and uses CFormsII API so you can edit it easily yourself)
</li>
<li>
Full range of formatting for widget layout in Admin -> Options -> Quick Shop
</li>
<li>
Shopping cart Widget
</li>
<li>
Checkout page
</li>
<li>
Ability to create different product options in a drop-down
</li>
<li>
WordPress MU compatible
</li>
</ul>
One of my clients required a quick and dirty shopping cart for WordPress. The background:
<ol>
<li>
They had more than one product per post
</li>
<li>
They only wanted orders to be sent via email
</li>
<li>
They only needed EFT (Electronic Fund Transfer – like Direct Debit or Internet Banking)
</li>
</ol>
Thus, Quick Shop was born thanks to the excellent way in which the WordPress Plugin API is set up.
List of possible future features:
<ul>
<li>
AJAX implementation
</li>
<li>
Inventory quantities
</li>
</ul>
Please be aware that I’ll only be updating this if I need to or if I’m paid to. Feel free to come on board and contribute!

Quick Shop

Quick Shop is a Wordpress Shopping Cart with both Paypal and Email functionality built-in.

Simple Seller vs Quick Shop