There is a tutorial for SL'ers that shows manipulating the UVMap mesh itself. Because of a quirk in SL one often needs to do tweaks to the UVMap. So, they show how to do things with the UV that few others show. Knowing how to work with the UVMap mesh can come in handy. I had not realized the UVMap mesh was editable. Another Duh moment for me.
Ignore their references to SCULPTIES. Just think of them as a 'special mesh' for use in SL. They are just a mesh that is a specific vertices count surface to allow the baking of the image one imports to SL. Other than that they are just like any other surface or object one would make and texture.
They have an tutorial on using the Node Editor. First one of those I've seen. They use it to bake a texture. I think it is in the Nurbs tutorial. I forget.
A video tutorial is here: http://blog.machinimatrix.org/2008/05/12/blender-surface-textures/#more-12
A more complex one: http://blog.machinimatrix.org/2008/09/01/texturizing-with-multiple-images/