Upspring
Note: Upspring will hopefully be soon deprecated. The next engine release will contain assimp which allows to load different model formats directly. see forum for more details.
Upspring
Upspring is a Model Converter/Editor for the Spring RTS Engine.
It can load and save .s3o .3do .3ds .obj .opk .c3o files, the first two of which are used by the Spring engine.
Argh's UpSpring Easy Workflow Guide
Download
Source Code: https://github.com/Kaylewt/upspring (should compile on win32 and linux)
Win32 installer: http://user.supradigital.org/jcnossen/UpspringInstaller-1.54.exe
mirror on springfiles: http://springfiles.com/spring/tools/upspring
mirror: http://www.warriorhut.org/spring/tools/modelling/UpspringInstaller-1.54-EulerAngles.exe
Known bugs
Upspring's useability is so-so and there are also some bugs you have to live with. Luckily, there are more annoying than fatal, some are listed here:
http://answers.springlobby.info/questions/690/why-does-upspring-mirror-my-model-when-i-import
http://answers.springlobby.info/questions/398/upspring-how-to-set-piece-origin