Away3D is an open source 3D engine used for the creation of 3D content on desktop and mobile platforms.
It is written in AS3 and is compatible with the Adobe Flash and Adobe AIR platforms.
Main repositories:
Core lib: https://github.com/away3d/away3d-core-fp11
Core examples: https://github.com/away3d/away3d-examples-fp11
Main resources:
Tutorials: http://www.away3d.com/tutorials