Blender is a free downloadable opensource 3d package that can match it with the big boys like Maya, 3ds Max and XSI.  Blender has an exceptional quality toolset, that can be seen in the short film Big Buck Bunny. Blender's other advantages include a huge support community and tutorials, regular updates and bug fixes by the army of people working on the project.

More info at wikipedia.com

Company: Blender Foundation (opensource)
Focus: Highend 3D General

Blender.org

Blender is free so it doesn't require a demo version, get it here.

Blender will run on Mac PC and Linux, for full details go here.

free