Fleeble4 is a java-based agent framework. Its current primary purpose is as an educational tool.
Fleeble4 has been developed by Reinier Zwitserloot and Robbert Jan Grootjans as part of a research project at the Delft University of Technology, supervised by M. Pantic.

Fleeble4 is available for Mac Os X, Windows 2000/XP, and x86 Linux. Separate installers for the listed operating systems are available.
You need A Java Development Kit v1.5 (also known as J2SE5.0). For linux and windows, you can go to Sun's java site to download it. For Mac Os X, head to Apple's java site.
Once its installed, download fleeble from the downloads page.

Fleeble4 is equipped with extensive help features, including a tutorial that shows how to create agents.
Access it by selecting the Help feature from the menu.