Shopify App Store
The Shopify App Store is a collection of free and premium plugins that extend the functionality of your online store. It is a great way to adding more specialized features to Shopify.
Add your own features
With the Shopify API you can add new functionality to Shopify yourself. You can use your favorite programming language to create new apps for your online store, and you can even share them with other Shopify merchants on the App Store. All you need to get started is a Shopify Partner account.