Have a look at the features of your modeling software. Most of them also have UV tools onboard. Which allows you to skin your mesh.

For models with lots of faces you may want to have an unwrapper. Not all Modeling software has a good working unwrapping feature.In this case Ultimate Unwrap jumps in my head here. http://www.unwrap3d.com

Or the Blender internal unwrapper as a standalone. Roadkill. http://www.pullin-shapes.co.uk/page8.htm

For the texture part use your favourite 2D software ...