App Inventor is a blocks-based programming tool that allows everyone, even novices, to start programming and build fully functional apps for Android devices.
With App Inventor anyone could be a mobile developer and have his first simple Android app in less than one hour.
App Inventor provides to “developers” two types of interfaces, called a Designer and Blocks.
In the Designer screen the user can manage the visual part of the application, defining the screen layout and placing the various components with a simple drag-and-drop. For each component it’s also be possible to set a number of properties.
In the Blocks screen is use instead for manage the logical part of the applicaione, defining the behavior through the use of visual blocks, as if they were Lego bricks to be joined together.
Once completed the application the user will be able to test it with his device or with the emulator.
App Inventor is available at this link http://ai2.appinventor.mit.edu/