Voxel based rendering

I’m new to the net, never realy found the perfect service provider, so I might be up-to-date about this.
But does anyone know how to do Voxel based rendering?
This has grown to be an interest of mine since I have seen Voxel engines outperform polygonal engines with a factor of one to a hundred. Can anyone give me a pointer to where to get info on this subject, or can anyone explain how a Voxel based 3D engine renders?

Head over to www.flipcode.com they have great tutorials about voxel engines.