GMO

GMO is a file format commonly used in PlayStation Portable games. It can contain model, animation and texture data. Files of this format always have a .gmo extension.

Noesis
Noesis is a free tool for viewing and converting between hundreds of model, image, and animation formats. It utilizes a robust plugin system, with support for native extension modules and Python scripts.

Noesis is a helpful tool due to its simple GUI.

Noesis allows you to convert GMO files into many common model formats. It also includes a batch option.