It's not that's cold really (now that we're Minnesotan), but we aren't taking any chances. Our inauguration gear includes:
1 bottle of water each
Camera, 2 extra batteries, 1 extra disk
Phones - Ellen's doesn't work on the Mall, but Dave's sometimes does - texting most reliable
Lightweight blanket from JazzFest which can serve as a poncho in case it rains (no umbrellas allowed).
Ellen is dressed to go skiing but without the goggles and skis.
Awesome socks from Minneosta mohair farm: http://www.austinsmohair.com/
Ski bibs (fashion sense is long gone)
Ski gloves (in case it's really cold) and regular gloves
Full wool ear-flap hat
Dave has on 2 hats (one with ear flaps), long-johns and jeans had cold toes after a while.