A recent Nova included an interview with the astronomer who discoverd the first 3-planet exosolar system. After the public announcement, she received a letter from a 4th grade class who asked the same question about planet names, and had suggestions for the new system. Two were gas giants, twice and three times the mass of Jupiter, and the third was small and orbited close to its sun. So they came up with these names: "Twopiter", "Threepiter", and... "Dinky".

A bit hard to generalize, but I like them. =D>