To get you started Perfecto,

1. Take a sphere and planar make the top 15-25% of the polar faces.

2. Take a planar or cylindrical map of the remaining center section faces.

3. using cut uv's cut a seam up the side of the center section in the UV editor.

4. select all the uv's in the center shell and then right click the unfold icon to bring up it's options. Uncheck everything and select constrain horizontal and then unfold, then select constrain vertical and unfold. That should get the center section unwrapped pretty nicely.

Then you can unfold the pole caps and texture pretty smoothly across the center section.

You will get something like this. I hope the image is not offensive, I have been playing with aircraft nose art and the image was handy.



This is just one approach to doing a sphere to render the center section pretty soothly. For a full pole to pole render it is trickier to get a distortion free mapping.