Ben Huson

This plugin displays cross sales in WP e-Commerce. It provides the same functionality as in earlier versions of WP e-Commerce plus a little bit more.
Doesn’t do anything yet but will replace the current WP e-Commerce ‘also bought’ functionality in version 3.9+
New features include:
<ul>
<li>Option to set cross sale image sizes.</li>
<li>Remove hardcoded styling so it’s easier to style via css.</li>
<li>Improved code structure.</li>
</ul>
PS: You’ll obviously need WP e-Commerce installed for this to do anything 😉

WP e-Commerce Cross Sales (Also Bought)

This plugin displays cross sales in WP e-Commerce. It provides the same functionality as in earlier versions of WP e-Commerce plus a little bit more.

ChrisHurst

MyWebsiteAdvisor

Allows for Free Checkout with WordPress e-Commerce Plugin. 
Can be used with 100% discount coupons and $0.00 products. 
When the cart total is $0.00 the payment form will be replaced with the text ‘Free Checkout’ and offsite checkout will be skipped.
Developer Website: http://MyWebsiteAdvisor.com/
Plugin Support: http://MyWebsiteAdvisor.com/support/
Plugin Page: http://mywebsiteadvisor.com/tools/wordpress-plugins/wp-e-commerce-free-checkout/
<a href="http://mywebsiteadvisor.com/tools/wordpress-plugins/wp-e-commerce-free-checkout/" rel="nofollow ugc">Premium Version with Advanced Features</a> including:
<ul>
<li>Available To Members Only Option.</li>
<li>Available Only To Specified User Roles Option.</li>
<li>Hide Billing And Shipping Address Forms.</li>
<li>Customize the ‘Free Checkout’ Message on the Checkout Page.</li>
<li>Lifetime Priority Support and Updates!</li>
</ul>
Learn More Here: http://mywebsiteadvisor.com/tools/wordpress-plugins/wp-e-commerce-free-checkout/
Requirements:
<ul>
<li>WordPress</li>
<li>WP e-Commerce Plugin</li>
</ul>
To-do:

Name: WP e-Commerce Free Checkout

Allows for Free Checkout with WordPress e-Commerce Plugin.

WP e-Commerce Cross Sales (Also Bought) vs Name: WP e-Commerce Free Checkout