For parking at the Philadelphia Airport I recommend Kinney Airpark (215-492-5353). It is a parking service located near the airport. They have a fast and dependable airport shuttle from my experience using them 5 different times. I used them this year and they charge $6.95 per day for a AAA member and the 7th day is free. They are easy to find on Essington Avenue with a big sign for the place.

I agree with Brian that the Amtrack from 30th Street Station in Philadelphia to New York City is a good public transportation choice.

Ed Wickham Glenside, PA