Amtrak www.amtrak.com is the American national public rail system. The trains depart from 30th Street Station and take 75-90 minutes to reach New York. There are two trains, "regular" and "Acela." The coach class fare on regular trains can be purchased for between $45 and $75 per ticket, one way, depending on the train. The cost of the Acela is $110-125 one way. This train is faster than the regular train and mainly used by business travelers. For non-business travelers, the extra cost of the Acela train is not worth the 10 minutes of time savings. Amtrak trains are "all reserved" which means you must have a ticket for your train in advance; seating is on a first come, first serve, basis. Check the website for discounts and "hot deals" expecially for weekend travel.
Another rail option is to use the two local public transit systems: SEPTA www.septa.org and New Jersey Transit www.njtransit.com. At 30th Street again, find the NJ Transit ticket machine next to the SEPTA ticket window. Purchase a ticket from 30th Street Station to New York Penn Station (*not* Newark Penn Station). Round trip tickets are about $30. Take SEPTA's R7 train to Trenton, New Jersey. Then transfer to the NJ Transit train which is usually in front or across the platform, but not always. (You may want to go to www.septa.org to look at the R7 schedule to confirm which trains connect with NJ Transit.) The whole trip is usually just over two hours, but can sometimes be as long as three hours, depending on the schedule of the NJT train. For those who don't mind the extra time and hassle of changing trains in Trenton, the savings of about $70 round trip is worth it. Depending on where you are staying, you may also find it useful to take the R1 SEPTA train from the airport to Center City . However, for the relatively short distance between Philadelphia and NYC of about 1.5 hours, the cheaper option is the bus.
Greyhound www.greyhound.com is the largest private bus service in the country. They are located at 10th and Filbert near the Convention Center and Chinatown . They offer non-stop trips to New York as low as $34 one way online although you can purchase them at the bus depot. It's about a two-hour ride.
There are a number of small bus services in the Chinatown area that offer service to New York. Besides the companies listed on broadwaynyc's link, there is also New Century Bus www.2000coach.com. Fares are about $24 round trip to NYC's Chinatown. Inexpensive bus service to NYC is also offered by Megabus and Bolt Bus https://www.boltbus.com/default.aspx. These two companies offer service to the NY Penn Station vicinity which may be more convenient for tourists than the Chinatown bus which only goes to Chinatown.
** Note: The original information for this thread came from the following forum thread: