Blender 3D, with it you can model, UV map and Sculpt (create morphs) all in one for free.
A Paint program like GIMP.
VSS for easy materials manipulation not only skin.
A lot of useful Python scripts I've found for free all over the web.
CR2 Editor or CR2 creator for editing your poser files without lossing your mind in a text editor
Morph Manager
Apollo Maximus: you can get almost whatever creature you can imagine from him whith a lot
 of clothes, and nobody knows for how long he will be available.
Imagination :-) (most of the fun part is to create not to buy, whatever the result you get)