The intriguingly named Ignis Fatui screensaver displays an impressive moving system of light particles to create a drifting effect across your screen.
Previously it was rather too heavy on RAM for a screensaver but the developer has now fixed this memory leak problem, so it shouldn't sap too much of it. There are a handful of options that allow you to control how the particles circulate, the colors of them and size and speed of them on your screen. Note that, unfortunately, Ignis Fatui doesn't yet work with Snow Leopard due to changes Apple have made to the screensaver engine.
Ignis Fatui is a soothing screensaver for all those that like light particle effects on their screen.