Fuse - Fuse is a UX tool suite for mobile app designers and developers.
Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Dropsource - Mobile development platform for building native iOS & Android apps
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Siberian CMS - Siberian is an Open-Source and Free App Maker. Unlimited Push Notifications. Unlimited features. Fully Customizable. Download it and build your own app now!
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.