Here is a list from About.com of local places with beautiful Christmas light displays:

ZooLights at the National Zoo
Rock Creek Park. Washington, DC. November 23-December 9, Friday, Saturday and Sunday only. Open nightly December 14–January 1 (except Dec. 24, 25 and 31). The National Zoo presents a seasonal display of thousands of sparkling animated lights, winter-themed crafts, ice sculpting demonstrations, choral groups, and storytellers. See Photos of ZooLights

Festival of Lights at the Mormon Temple
9900 Stoneybrook Dr., Kensington, Maryland. (301) 587-0144. November 30, 2012 – January 1, 2013. Dusk to 10 p.m. nightly. Nativity scene is open each evening from 6 to 9 p.m. Live musical performances begin at 7 and 8 p.m. See Photos of the Mormon Temple Festival of Lights

Winter Festival of Lights at Watkins Regional Park
301 Watkins Park Drive, Upper Marlboro, Maryland. Friday, November 23, 2012 through Tuesday, January 1, 2013. HOURS: 5-9:30 p.m. daily. $5 per car;  $10 for multi-visit passes for cars and vans (good for three visits). The festival is FREE on December 25. You may bring canned food items to donate to local food banks for the holidays. Winter Festival of Lights is Prince George’s County, Maryland’s spectacular drive-through Christmas light display featuring more than a million twinkling lights. See Photos of Winter Festival of Lights at Watkins Regional Park

Symphony of Lights in Columbia
Symphony Woods, Merriweather Post Pavilion, Columbia, Maryland. (410) 740-7840. November 19, 2012 – January 6, 2013. Hours: Open 7 days a week from 6-10 p.m., including holidays except CLOSED December 31st for the Midnight at 7 event. $20 per car. Symphony of Lights is a spectacular drive-through display of more than 75 animated and stationary holiday lights. All proceeds from the Symphony of Lights benefit the services of Howard County General Hospital. See Photos of the Columbia Symphony of Lights

Lights on the Bay at Sandy Point State Park
Route 50, Annapolis, Maryland. (410) 481-3161. November 19, 2012 through January 1, 2013, 5-10 p.m., 5-10 p.m. An annual scenic drive through holiday lights show sponsored by the Anne Arundel Medical Center. Drive along the shore of the Chesapeake Bay and see more than 60 animated and stationary displays illuminating the roadway. $14 per car. See Photos of Lights on the Bay