Speaking about 3D in flash environment many examples, experiments and libraries are around to play with them,impossible is not to mention:
The famous Sandy3d

or the nice
Away3d

or the more famous Papervision3D that now got also a blog for developers

and the new Paperworld3D as linked here that mix Papervision and red5 for multi player experience
or the promising Wow-Engine that implement also a physic engine
Now the new flash player 10 is (finally:)) starting speaking about 3d but as many are saying is not exactly a “real” 3d but indeed a sort of 2.5D (as someone defined it), it got just some tool to start playing easy with some 3d toys, but the new features and the faster routines of the new flash player 10 are now begin used , and in particular by this new promising 3d engine:
ALTERNATIVA 3D now at the milestone 5.0
here some of the best features of this great Russian as3 engine:
* Signals system — only necessary calculations;
* BSP — quality polygon sorting, “sharp” crossings;
* n-gons support;
* reusing layers (redrawed only changed regions, independent polygons);
* objects hierarchy;
* only necessary matrix, coords and UVs recalculating;
* perspective correction — dynamic triangulation;
* collision detection.
And for the future releases:
* dynamic lighting and shadows (point and directional lights);
* bump lighting;
* parallax mapping;
* automatic UV-mapping;
* sprites, 3D-sprites;
* sprite lighting;
* texture objects;
* Global Illumination imitation;
* sprite pre-render system (phases render on server using uploaded 3D-models);
* animation system (including inverse kinematics);
* 3D-objects interactivity;
* physics simulation.
here you can find some great demos:
(you have to be flash player 10 installed in order to see the fp10 optimized version)



stay tuned at the official
Alternativa 3d blog
and follow the story of this promising new Engine for flash!