Add Blender, an all-in-one tool for 3D works, to your "Game Development Kit"-Site
Blender is an extremely powerful (and free!) tool to work with 3D stuff, including among other Modeling, Materials, Rigging, an Animation Toolset, Sculpting, UV (Un-)Wrapper, it has tools for Game Creation and also allows to port models in both .x and .fbx format (the latter with an easy-to-install plugin).
It's just awesome and I whonder why it is not mentioned here.
Maybe because it's difficult to master?