Well there is Autodesk but it will set you back several hunderd to a thousand dollar, but if you are going the cheapest, study the mesh files and get out your notepad and start playing around with the numbers and the code

Photoshop CS4 is also very helpful. Or GIMP with the DDS plugin.

another free one is GMax, though there will need to be a maxscript for mesh import/export created (i've tried once, it's not that easy). GMax is essentially a free, dumbed-down version of 3DS Max 4 or 5. Another one you might look at is Wings3D, which I hear is very well liked by its users. another one for skinning- Blacksmith3D, which allows you to paint your materials directly onto the model surface. Note that I haven't used Wings or Blacksmith, but from what I hear it's a very reputable and well liked program.