I've complained a few times about my crappy scale. And while the scale is still crappy (it will give me 5 different weight readings within a 5 minute period) I found this article on weight fluctuation very fascinating. Some of it was info I already knew in general but this goes into more of the technical/scientific aspects.
So good stuff to read on a day when I want to throw my scale out the window.
What the Number on the Scale Really Means by Richard Talens