Obligatory note re: standing desk ergonomics: http://ergo.human.cornell.edu/CUESitStand.html
The lesson seems to be to mostly sit, but stand and walk around every 30-45 minutes or so.
Thanks for the link! The page's arguments don't seem to strongly support its recommendation to spend most of the day sitting, though; my takeaway is that you should look at ergonomics, and you shouldn't stand all day.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.