Multimedia authoring tool, especially suitable for educational purposes

Squeak
Free
Offline
http://www.squeak.org/

Squeak is a modern, open source, full-featured implementation of the powerful Smalltalk programming language and environment. Squeak is highly-portable, running on almost any platform you could name and you can really truly write once run anywhere. Squeak is the vehicle for a wide range of projects from multimedia applications and educational platforms to commercial web application development. Read on and join in!