In no specific order and not a full list, this we have only added to a bit here and there when we have had time.

All 3D models regardless of program used must be able to export to the Collada format.

Blender - Open-source 3D modeling program that comes with built-in support for COLLADA.

Gimp - Open-source image editing.

Paint.NET - Closed-source free image editor comparable to GIMP but easier, smaller, faster

Audacity - Multi-channel sound editor.

OggDropXPD - Drag'n Drop your audio files to convert them to .ogg.

notepad++ - Advanced text editor, crucial for script writing.