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Below are images of triangle meshes that approximate spheres.  The last "globe" image is actual sphere geometry.  I used the algorithm in the OpenGL "Red Book" (Chapter 2) for sphere generation by icosahedron subdivision.  In my opinion, this subdivision looks better than the tetrahedron subdivision described in Edward Angel's Interactive Computer Graphics text.
 

Sphere Approximated by 80 Triangles
400x400 JPG converted from 500x500 PPM output
Total time to parse, build, render and write: 2.265 seconds.
 

Sphere Approximated by 320 Triangles
400x400 JPG converted from 500x500 PPM output
Total time to parse, build, render and write: 2.953 seconds.
 

Sphere Approximated by 5120 Triangles
400x400 JPG converted from 500x500 PPM output
Total time to parse, build, render and write: 4.328 seconds.
 

Texture Mapped Sphere
400x400 JPG converted from 500x500 PPM output
Total time to parse, build, render and write: 0.672 seconds.
 

Pool Anyone?

Ok, so I couldn't resist the temptation to try and make something that looks real.  Since I only knew how to texture map spheres I decided pool would be ideal.  I think we do motion blur later, so it'll be nice to get back to this model then.  The texture maps were created in Adobe Photoshop from digital images of real pool balls and a real pool table surface (courtesy of my brother Jonathan).   Yes, I realize that the stripe of the 13 ball is a little off, but do you have any idea how hard it was to create that image?
  

Texture Mapped Objects
JPG converted from 700x500 PPM output
 

Problem and Resolution:
Tessellated Texture Coordinates

The earth images above that you're seeing are focused on North America for a reason (and it's not that I just favor that continent): the back sphere...where the texture wraps around had a problem.  My model file contains the (u,v) texture coordinates for each triangle.  These coordinates are generated in the same manner that the (u,v) coordinates for a texture mapped sphere are generated.  Values are in [0,1].  The problem with a tessellated object is that if a triangle has coordinates that "wrap around" (i.e. the u coordinate goes from, e.g., 0.9 to 0.1) we don't actually want all the texture between 0.1 and 0.9...which is the way the renderer sees it.  The renderer has a way to wrap around, but it needs a (u, v) outside [0,1] to do so.  The solution was to modify my tessellated sphere generator, detect when this situation occurred, and add 1.0 to the value that should wrap around.  Below are cropped images of the 'back' of the tessellated Earth image, before and after.