Scratch - Scratch is the programming language & online community where young people create stories, games, & animations.
Blockly - Blockly is a library for building visual programming editors.
Tynker - Game Worlds for Kids to Learn Programming
EduBlocks - Making the Transition from Scratch to Python easier.
RoboGarden - RoboGarden provides a complete, game-based suite that teaches coding from beginner to professional level, starting with block programming and progressing to professional Python and JavaScript programming.
Snap - Snap (formerly BYOB) is a visual, drag-and-drop programming language.