Blender 3D Software

Blender is the free open source 3D content creation suite, available for all major operating systems under the GNU General Public License.

It is available from http://www.blender.org

The default install includes many exporters, unfortunately the only Cal3D exporter included is for xml files, which are not useable by Moviestorm.  However, a Moviestorm exporter is currently a work in progress, the alpha version was used to create most of the props in this addon.
If you are willing to experiment, a beta version (0.12) of the Blender Moviestorm exporter is available: export_moviestorm.zip

Learning Blender
User Manual
Blender Noob to Pro Wiki
Document and Tutorial links

Using the Moviestorm Exporter
Creating Bodyparts in Blender
Weighting Bodyparts in Blender
Exporting from Blender to Moviestorm