Stay away from the DC area between 6:30AM - 9:30AM and 3:30PM - 6:30PM. You will be a much happier camper.
Take 95 South straight out of Baltimore, and follow the 95 South side of the DC Beltway (East side of city). Cross the Woodrow Wilson Bridge, and soon after you will hit the 'Mixing Bowl' to head South down 95 toward Richmond; getting off of the DC Beltway. You will see signs for 395, 495 and 95 South. Follow 95 South; which will be a huge fly-over, lots of construction, and you may see some traffic around here, but its not worth getting off if you do not know the area. Good luck.