One of the extensions that I love working with at WooThemes is the Subscriptions extension for WooCommerce. It's probably the most complex extension we have which can make troubleshooting issues challenging but that's offset because the developer also has the best documentation bar none.
The number of possibilities with Subscriptions are really endless. One of my favorite examples is HDPiano.com which sells virtual memberships to learn how to play piano. There's also plenty of users who sell tangible products each month. I just ran into a user who creates fancy shipping labels in Photoshop and uses those labels to ship her products.
The only problem in her case was that she creates the shipping label before the new order comes in so she needed a way to be notified of a customer changing their address before the actual order came in. This is where some of those awesome WooCommerce hooks come in.




