One key feature of the nopCommerce is its pluggable modular/layered architecture which allows additional functionality and presentation elements to be dynamically added to the application at runtime. nopCommerce plugins allow users to easily customize & enhance any nopCommerce based store site. Instead of customizing the nopCommerce core to add a new feature to the site, developers can create a plugin to extend the functionality of nopCommerce.
I have posted an article on steps involved in creating a nopCommerce plugin, please see: http://www.strivingprogrammers.com/Blog/post/Lavish-Kumar/2122/Beginners-guide-to-nopCommerce-plugin-development-ASP-NET-MVC-based-e-Commerce-solution/
nopCommerce Version: 3.70
Hope it helps...