A related posts plugin that works quickly evenShopp Improved is a plugin that extends the popular Shopp eCommerce solution for WordPress. Requires PHP
I recently worked on a site where I used the Shopp WordPress plugin to set up E-Commerce. The first big issue that I ran across was allowing for user customizations of products. For example, if a product can be engraved with a name, includes the person's initials, can include a message, etc. Shopp does include the ability to add these kinds of user input fields, but it's done through a template tag. This means that you either have to apply it to all items, or you need a developer to set it up on a per-product basis. My client has quite a few products that are custom-made, and they really needed to be able to set up these fields themselves.
In comes Shopp Improved. It creates a user interface to allow you to easily add these fields to any product. The inputs can then be easily integrated into a shopp product template with just a couple lines of code.
Requires PHP 5+.