Away3D

Away3DÂ is a powerful realtime 3D engine for Flash. Some features:

Import/export of several popular formats, including animated meshes;
25+ useful primitives and a solid selection of material types that you can easily extend yourself;
Several renderers offering varying degrees of complexity vs speed;
Solid Actionscript API that is now in the fourth iteration. Version 4.0 and upwards will support the Stage3D API (aka Molehill) taking the rendering from the CPU to the GPU. This will enable polycounts that are in the millions rather than the 4-8 thousand that are possible with the Flash Player 10 version of Away3D;
Materials/Shaders: Color, bitmap, phong, outline, flat, video, enviro, bump/ normal map, fresnel, glass, lambert, surface scattering, shadow / light maps and more;
Cameras: several Camera types such as free, target, hover, chase, Camera lenses (ranging from fisheye to isometric);
Lights: point, ambient, directional;
Primitives: standard primitives include Cube, Sphere, Cone, Cylinder, Torus, Billboard, Planes and many more. All the way down to LineSegments to Triangles, allowing you to construct any primitive yourself;
Clipping: rectangle, nearfield, frustrum;
File import: ASE, AWD, 3DS, MD2, Collada, MQO, KMZ and OBJ;
File export: AS3 class, AWD, Elevation2AS3 and OBJ
Mesh modifiers: Align, AlignToPath, Explode, Grid, Merge, Mirror, Replicate, Weld;
Mesh Extrusions:Â Lathe, Path, Segments, Elevation;
Utilities / debug:Â FaceLink, Trident, Normals display;