not sure if it´s been posted before,- but I just discovered this project lately and I like the approach much much more as the others as the developer actually shows very nicely what he did and what changes are made- in some cases even how. It´s based on the papervision engine but has a lot improvements on depth sorting (by splitting the mesh), perspective correction (dynamic mesh tesselation, level of detail,...), smoothing textures and very nice sprite support like in doom 1&2.
Sandy btw. is about to port the engine to AS3 as well and at least they say that their´s should be faster as pv and this away3d as the architecture is much more simplified and has less features as the 2- but that is nice to as it there would be another engine that perhaps can boost more objects.

here is a current overview demo of away3d:
http://away.kiev.ua/away3d/techdemos/engine/
which should introduce you in what it differs from the others

new homepage:
http://away3d.com/

documentation:
http://away3d.com/docs/

downloads:
http://away.kiev.ua/away3d/techdemos/
(click on sources to download some of the examples)

and just to give another candy,- here is a 3dsmax plugin that generates AS files (AS3 classes) on the fly for papervision, sandy, and away3d of your model and UV data. That way the mesh doens´t need to be parsed and just can be placed as new instance in your main class.
the url:
http://www.dreammania.net/showcase/a...s-max-english/

oh and remeber, 3d is not everything but it is a hype