Getting to DC
While it may seem obvious, if you haven't booked airfare for Inauguration weekend, do so ASAP! With the hype surrounding this weekend coupled with the holiday season, rates are bound to sky rocket. Book your flights NOW! The closest airport to Washington, DC is Ronald Reagan National (DCA) but depending on the rates, Dulles International Airport (IAD) or Baltimore-Washington International (BWI) are also close enough for them to be an option.
Train is great if you are on the East Coast - if you are in NYC or Philly, the Acela Express is a breeze.
Car - either yours or a rental, driving may be the most affordable, especially if the low gas prices hold. Driving is actually perfect if you plan to bring the whole family and need to cut back on the expense of flights.
Bus - there are PLENTY of churches and organizations planning bus trips. Keep your ears peeled for one being organized in your city. Try Inauguration Road Trip's super cool Road Trip for Change website to connect with transportation from all major cities.
Metro - DC's underground train system will be the best way to transfer in/out of the city for all Inauguration events. Buy or load your SmartTrip tickets early to avoid the lines! Info on using DC's Metrorail system can be found on About.com
Hotels - By the time you read this, every hotel in DC and 25 miles out is sold out....or too expensive to even consider. If you are lucky enough to find something "affordable", book it ASAP! Check here for hotel rooms that may be available: http://www.washington.org/visiting/experience-dc/presidential-inauguration/information
Family/friends - Think of everyone you know in the DC Metro, Richmond and Baltimore area. Don't be too shy to call on family, friends (even those long lost college alum) to bum lodging for the weekend! Just be sure to offer a donation to the hostess ;)
House rental - There are plenty of folks renting out their homes, apartments, and timeshares for inauguration visitors. Visit these sites for private rentals OR if you'd like to share your place:
Several sites have dedicated Inauguration packages...don't scream at me when you see the prices ;)Inauguration activities.