If you're teaching about the presidency, you'll love these. First is the Washington Post's POTUS Tracker. It displays the president's daily schedule in convenient graphical form, so you can see how much attention he devotes to which issues and which members of his administration. Biggest surprise: Malia and Sasha get more face time than Rahm or Pelosi. I guess sometimes family comes first.
I also wanted to recommend Seth Hill's graph of American military fatalities. Biggest surprises: the lethality of the Korean War and the weirdly symmetrical curve of Vietnam fatalities.