This started off as an uninspired PaD. I had hoped to check out my 1000x ND filter on a river this afternoon, but we had snow/rain and that would really affect the shot (so I think).
I was walking around the house looking for something and I decided to try some smoke shots. I set up a white background on our kitchen table, broke out the tripod and went to work. I realized early on that this wasn't to be (like 7 shots early). I grabbed a cereal bowl and filled it with water and dropped a blue marble in for a bit. My 10-year-old came by and helped, though she had some trouble tripping the shutter with the remote release cord.
I had two strobes, the 580EX-2 on camera, bounced off the ceiling and my 420EX to camera left with a paper towel wrapped around it to diffuse the light. About 150 photos and 45 minutes later, I had switched to a clear bowl and a black background. This still isn't perfect, but it is much better than the first set. I actually have the timing down quite well, I know when to trigger the shutter/strobe after dropping the marble from a height of about 18".