Maybe everyone else already knows this, but I just learned it: If you put a raisin in a glass of champagne, it will sink, then float, then sink, then float, ad infinitum (or until you just drink the champagne already). It has to do with all the wrinkles on the raisin, which provide extra surface area of the champagne bubbles to attach to. When the raisin reaches the surface, the bubbles pop, the raisin sinks, and the cycle starts over again.
Having tried this at a restaurant recently, I can report that the effect is utterly (if somewhat pointlessly) mesmerizing, sort of like a very low-tech lava lamp.
Food is fun!