Took a colour changing lightbulb and put it into a sealed empty Pringles can. Suspended this from a frame by the power cable. Made a small hole in the Pringles can for the light to come through. Pointed camera upwards and took a long exposure of the swinging can whilst changing the colour of the lightbulb using the remote. Really happy the way it turned out. (Was the third attempt after trying with laser pens, etc.) It really simple to set up and you can generate a lot of different effects.
I always wondered why barred spiral galaxies have the bar. This effect makes that really obvious. Looks great too!