If I worked in DC, I'd be taking that day off for sure. What a mess that place will be.

For starters...all bridges from VA to DC are closed. Good luck!!
http://www.nbcwashington.com/news/local/DC-MD-VA-Release-Inauguration-Transportation-Plans.html
I've posted about the bridge-closings elsewhere on the DIS, but I'll repeat what I've seen/heard about getting around the DC area on Inauguration Day.
*-The Potomac Rover Bridges that are between DC & Virginia will be closed to INCOMING traffic. They will be OPEN to buses and OUTGOING vehicles.
*These same bridges will be open to *pedestrian* traffic where feasible.
*These bridges are as follows(in order from East to West):
1)14th St. Bridge Complex...first bridge-group North of Reagan/National Airport("middle" of Mall)...
I-395 & US ROUTE 1
2)Memorial Bridge...runs between Arlington National Cemetery and Lincoln Memorial (West end of the Mall)
3)"TR" Bridge [Theodore Roosevelt Memorial Bridge]...runs between Rosslyn and Kennedy Center...
I-66 & US ROUTE 50
4)Key Bridge [Francis Scott Key Bridge]...runs between Rosslyn & Georgetown (west perimeter of DC proper, NO METRO in Geo'town)...
US ROUTE 29
Some other tidbits:
*Do NOT count on getting parking at Metro lots. Btw, the parking is opening at 3AM Tuesday morning.
*George Washington Parkway ALREADY has Crowd-control fences installed in the median North of Alexandria. You will NOT be able to park on any frontage roads or west of the Parkway and walk directly across the Parkway, you WILL have to cross at the crosswalk.
*Pick one or the other to go to...the Swearing-In OR the Parade. You will NOT be able to attend both, the crush of people will be too great, movement between the two areas will be impossible.
*Bring cash. If you buy food/snacks/souvenirs, many vendors will probably not have cc machines. ATMs WILL run out of money. Bring small bills, exact change.
*Bring new $1, $5, $10 bills for the Metro-card machines (If you haven't bought needed card/s ahead of time.) The Metro-card machines are notoriously finicky.
Good luck,
agnes!