Well, I'm currently running an Eberron game. When that ends, the current idea is to run some classic modules - not sure what yet, but among the ideas that have been mentioned are Temple of Elemental Evil, Against the Giants, Expedition to Barrier Peaks, and White Plume Mountain. So, at least one of those, maybe more. Could certainly become a campaign, but it would also be there to give me time to do prep work for my next 'real' campaign. I have a few ideas bouncing around for that as well, such as:
-A Star Wars game set about a year after Episode III, with the players not strongly affiliated with the Empire at the start (though they could certainly go that way if they so choose)
-A game set in ancient Greece or in the Roman Empire, with lots of mythological monsters to be fought. Each nation would be ruled by a particular race - not sure on everything yet, and it certainly depends on what time period I go with, but I have a few ideas here and there. May use Iron Heroes for this, if I decide to go for a low magic feel. I came up with the idea before 300, but that'll be a good way to get a few of my players up for it
-A homebrew world I really need to do some work on, where magic is heavily tied to the nobility and there are real differences between nobles and serfs (who are allowed to adventure, they're just expected to tithe their lord, the lord of any lands they adventure in, the church... taxation when passing through a lord's land...).
-More Eberron, but with a different feel. Right now, they're basically a special ops unit for Aundair during the last years of the Last War. The next game is likely to be more real adventuring - dungeon delving, searching for lost treasures just for the sake of finding them (... and profit).
Of course, by the time I'm ready to run a new campaign, I'll have likely come up with at least another half dozen ideas.