Thanks to Ziggy for alerting me to this article! Very appropriate, given the day's events.
The Wik' has a list of US government officials in order of symbolic precedence. (They also have similar lists for other countries, but keeping with the rich heritage of my motherland, I don't give a crap about them.) This isn't the list of who is next in line for the presidency, it's just who gets dibs on riding in the cherry red vintage convertible for the parade.
One thing that surprised me while perusing this illustrious rollcall was that president pro tempore of the Senate is so low on the list; he's 23rd in symbolic importance. Compare that to speaker of the House, who is fifth. Senator Byrd follows the Secretary of Agriculture. He follows the drug czar. He's fourth in line for the presidency, but he's less prominent than the guys in charge of emotionally overwrought television ads about teenagers smoking pot and making sure organic beansprouts are really organic. (Maybe he should have stuck with being Exalted Cyclops.)
Of course, all of the aforementioned are less important than the mayor of the city in which the parade/ceremony/spelling bee/whatever is taking place. Which is humbling if you're a federal official and you happen to be in a ceremony in Muskogee, OK.