I think I learned this at a San Francisco Folk Music Club campout. I believe it was written by a park ranger: anyone remember his name? Is there another verse? I've messed with the words.

The Grateful Dead's Concert

If you go out in the woods today
You're in for a big surprise
If you go out in the woods today
You wouldn't believe your eyes.
For every head that ever there was
Is heading there this morning because
Today's the day the Grateful Dead give their concert.

If you go out in the woods today
You probably won't see deer.
It's not a park, it's a parking lot
With copious cans of beer.
Still we'll do the best that we can
To start a dead VW van
Today's the day the Grateful Dead give their concert.

(CHORUS)
Concert time for the Grateful Dead
The Grateful Dead I said, they're gonna be cranking up today
See the deadheads still in bed
We need the campsites, it's a holiday.
Try to roust them, go ahead,
Try to collect from them, they'll say that they have no dough
But at five o'clock you'll find them at Stanford
Standing in a line
To give their bread to the Grateful Dead.