[Carnage]

I'd personally go for doing it as a set of content types. Have a read at the blog posts on vb.com on how to write widgets and content types. You will need:

A content type to represent items in your shop; to add an item to the store you just post a new item of this type. It'll need similar things to the article type for adding a description and images, plus some custom fields such as price, quantity etc.

A widget to display the users shopping basket.

Some custom code to handle adding items to a basket, removing them editing their quantities and checking out. You should take a look at how paid subscriptions are handled; you may be able to reuse some or all of that code.

A method of notifying you of orders. This could be as simple as emailing you the order once its paid for. Or a complex admin cp to deal with it all.

I would be very tempted to try and handle the above two items by creating a second custom content type to represent an order. It would be posted automatically by checking out and only visible to admins+ The custom code for adding items to a basket could simply be actions on an order content type controller.

You may also need to override the default list controller so that you can sort things by price/ other custom fields.

This is a product I'd be interested in developing; however I've no time to do custom coding for at least 3 months.