After gaining a better understanding of particle systems and .particle scripts, I created a nice smoke effect. I find it alot more appealing than the current smoke effect sample included with Ogre. Perhaps this could be added to the next release of Ogre?
The main thing that makes the smoke look so good is the texture, which I have spent many hours playing with. There are many different ways to change the overall look of the smoke. Changing the opacity, contrast and brightness, etc. For example, try opening up smoke.png in your preferred image editor and inverting the color, then view the particle system in Ogre.
Then of course toying with the particle script itself can yield different effects. I have included the textures, particle script, and a code snippet in the following zip. There is some extra information that may prove useful in the ReadMe. Enjoy.
Particle_Smoke.zip dead link, but we contacted the author