Update:

Newer versions of Blender now come with a *Generate UVs* checkbox (that can do as the name says and provides pretty decent maps) when adding a new mesh for most of the objects. Simply access this from the <kbd>F6</kbd> menu or the toolshelf. *This option is only available when generating a new object*. The layout is below, still not perfect but useful nonetheless .

[![enter image description here][1]][1]

Add a _UV Sphere_ to the scene and select an edge with <kbd>Alt</kbd><kbd>RMB</kbd>, next enter _Face selection_ mode and select a face near the edge you marked. Next hit <kbd>A</kbd> to select the entire sphere and hit <kbd>U</kbd> _> Follow Active Quads_.

![enter image description here][2] 

*Note the grayed face near the middle of the sphere along the edge, this means that it had been selected before you selected the entire sphere and this is similar to what you should have done.*

After unwrapping, you should get a huge UV map in the _Image Editor_. Transform it as desired, I would recommend aligning one corner of the map to a corner of the image and scaling it via the _2D Cursor_.

![enter image description here][3]

A perfectly unwrapped sphere sans exponentially spaced UVs which aren't possible unless you tweak the map afterwards or modify the object's geometry.

![enter image description here][4]

---

You might notice a sharp seam near the top of your sphere where the texture stops. This is caused by the geometry of the sphere as the top vertices merge into a single point and the unwrap method basically ignores it.

![enter image description here][5]

To fix, just get an edge ring as close as you can to the middle vertex so that it won't be noticeable.


  [1]: https://i.sstatic.net/bUGRs.png
  [2]: https://i.sstatic.net/lkWVi.png
  [3]: https://i.sstatic.net/rSsMw.png
  [4]: https://i.sstatic.net/WiVAo.png
  [5]: https://i.sstatic.net/DyTHQm.png