If you're in to getting spooked and enjoy history, make sure you spend a night in Gettysburg, PA. The battlefield is open until 10pm and, whether you believe in ghosts or not, it's a *very* erie place at night.

Along similarly spooky lines near Philadelphia is the Eastern State Penitentary. It's one of those old, stone-cold prisons designed way back when cruel-and-unusual punishment was the way to go. After you leave, there's a few great watering holes a block away where you can talk about the chill going down your spine.

There's also several haunts in and around Lancaster, PA (Amish Country) if you're going out there.

I agree with everyone else about the budgeting and planning-- don't go overboard. I think a very rough plan is the way to go. Pick a few choice places and reserve your rooms in advance. These will serve to set the "milestones" for the trip and keep you where you need to be timewise. But in between those places, have some ideas on where to go/stay, but let the trip take its course. Excessive planning will get in the way, and you'll always be hurried and behind schedule.

Just curious: How long are you going and how much are you budgeting? Me and a friend hope to do 30-days PA-to-CA and back again on about $1500/each (lots of camping and cooking our own food, but with some splurging too)