Scratch is a visual based programming language. It was designed at MIT for teaching programming to children, but has become popular with young and old programmers. Some universities even use it as an introductory language for new students.
The latest version of Scratch, version 2, uses a web based interface. Unfortunately it is based on Adobe Flash and as such will not run on the Raspberry Pi. The Raspberry Pi instead includes an older version, based on version 1.4. The layout is a little different from version 2, but the functionality is mostly the same.