Update - May 6th, 2013: Tested and working with all Concrete 5.6 variants.
Do you want to sell products on your site and not need all of the features of a full-fledge e-commerce solution?
Paypal Cart Buttons allow you to do just that. Just add a block anywhere on your site where you want to sell physical products. Fill out the short form with your PayPal email address, price, handling and shipping information. This allows you to implement Paypal based e-commerce into any design with un-matched ease and flexibility.
This comes with two blocks, one for "Add To Cart" buttons and one for "View Cart" buttons so you can allow your visitors see the PayPal shopping cart at any point.