Blockly is described as 'library for building visual programming editors. Users can drag blocks together to build an application. No typing required' and is an app in the Development category. There are more than 10 alternatives to Blockly for a variety of platforms, including Windows, Linux, Online / Web-based, Mac and Android. The best alternative is Scratch, which is both free and Open Source. Other great apps like Blockly are Snap! (Free, Open Source), EduBlocks (Free, Open Source), Alice (Free) and Waterbear (Free, Open Source).
Snap! (formerly BYOB) is a visual, drag-and-drop programming language. It is an extended reimplementation of Scratch (a project of the Lifelong Kindergarten Group at the MIT Media Lab) that allows you to Build Your Own Blocks.
Alice is an innovative 3D programming environment that makes it easy to create an animation for telling a story, playing an interactive game, or a video to share on the web. Alice is a teaching tool for introductory computing.
Easy Programming for beginners. HyperNext Studio is an easy to use software creation system that allows hobbyists, students, educators, in fact almost anyone, to quickly start building their own software that works.
Bingo is a programming language based on Scratch by MIT which uses a "block" UI, where the user can snap together different blocks to make more advanced scripts. There are many added blocks to Scratch 1.4.
Visogram is a tool that lets you create user interfaces and graphical programs directly in your browser. Visogram is purely built on web standards: Interfaces you create directly become accessible by a broad variety of devices like smartphones - all they need is a web browser.