Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
GoodBarber - GoodBarber is a mobile app creation platform.
BuildFire - BuildFire is the easiest way for small businesses to build a mobile app in a matter of minutes for iOS and Android.
Fuse - Fuse is a UX tool suite for mobile app designers and developers.
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.
Dropsource - Mobile development platform for building native iOS & Android apps