Plate tectonics was going to be my next post, and I was hoping to find time this weekend/next week. That said, I've noticed that there's at least one other person (Hai-Etlik, I think) who's a real expert on tectonics, so hopefully there'll be plenty of additional comments on that one. It may have been a bit disingenuous to say that they're easy, though. I remember restarting a world three or four times because of plate tectonics, and eventually just giving up.