These sites all have e-commerce functionality to some degree. Some just have donation capability and others have full fledged shopping carts.
Drupal's Übercart suite of modules provides a good solution for doing online business. For e-commerce in WordPress I like to use the WooCommerce suite of plugins.
This is a very simple html e-commerce site that sells only one product.
This is one of the few sites that I a have done that I take credit for the graphic design. The design for this is minimalist bit I am happy with it.