Open Source Mobile E-Commerce App: MobileCartly
MobileCartly is an open source shopping cart application that focuses on mobile.
With a front-end that is compatible with all major mobile browsers and a powerful back-end, it makes selling via mobile pretty easy.
It uses a CSV file as the data source and you can use Open Office, Google Docs or MS Excel to add/edit/remove your products.
There are features like PayPal integration, order management, stats and invoicing.
It also has a WordPress plugin that can integrate your blog with the mobile store.