I've got my ongoing game in Sunset Valley, which has been modified beyond all belief (I've changed the buildings around and such), and I've got my Random Legacy for the forum, which is in Union Cove, but that's it. I've been meaning to start another town in Riverview for another game I want to play, but it requires a lot of building, plus, I wanted to completely rebuild Riverview or Sunset Valley, apart from the Rabbit Holes.
I've got all the expansions, which has five towns, plus Riverview, plus all three of the store bought towns, plus Union Cove, which gives me a grand total of ten towns to play in. I think I only ever touch three or four of them, but I've been meaning to change that.