I've been directed back to this post by Merlin Mann a few times now, but it hasn't gotten old yet. I love the way that he pins the idea of priorities up against the wall- inquisition style- and demands an answer.
Got news for you, Jack: if it moves, it's not a priority. It's just a thing you haven't done yet.
Making something a BIG RED TOP TOP BIG HIGHEST #1 PRIORITY changes nothing but text styling. If it were really important, it'd already be done. Period. Think about it.
I am so easily distracted. One of Merlin's recurring points is that you can't let yourself get caught up in the distraction of reorganizing and perfecting your system for prioritization. Any system has to simply get straight to the point.
So, if a mud room, or a crying toddler, or a CPR class, or even a short note from an old friend turns up on your radar screen today, don't ask yourself whether it's a "priority." Ask yourself what you must not do in order to make sure it gets taken care of.
At some level, if you are the sort of person that even cares about what things are priorities, the key is to really decide on what to do with things when they show up. Putting them on a list and stack ranking them has to be a very temporary exercise. In fact quite a few things probably don't belong on your list.
Maybe it will be helpful to think of that list as your This-has-to-get-done-today! list. Be really careful about what you allow in the same company with this stuff.