GuruBlog

for this animation I used a smoke sim and a volume material. The material only selects part of the density values using a color-ramp node. The smoke has no temperature difference but is moved by a turbulence force-field

you can download the blend file here

for this animation I experimented with a particle density texture and two different volume materials

you can download the blend file here

For this animation I used a volumentric material to simulate dust in the light cone of a spotlight

you can download the blend file here

for this animation I used the cell fracture addon to break a sphere and made the shards block the light paths of a point light inside a volume scatter shader

you can download the blend file here

For this animation I used the gooseberry-branch of blender 2.75. I made a volumetric material using the point-density texture node to create a cloud and added some red point lamps to a second particle sytem from the same emitter.

you can download the blend file here

If you want to run this blend file make sure you use the gooseberry branch of blender 2.75 - the point-density texture node isn't available in the stable branch yet