Quoted from weaverj:from dc: take 270 north, becomes 15 north (frederick), all the way to harrisburg. right before you get in town (camp hill), take harrisburg beltway west (581), then a little up the road get on 81 north. 25-30 miles up 81 it splits, take 78 east towards allentown. from there, you'll be flipping pinballs in about an hour.
no traffic/no tolls.
This is the way to go. Avoid 95 around DC and Baltimore like the plague