There are several new bus services between NYC and Baltimore, Washington DC and Philadelphia. The buses are new, fast, wifi enabled and generally just take a little more time than the train. The best part - the costs. My recent bus from Baltimore to New York City was $12 one way. The train: $103. Bus takes 3.5 hours, the train 2 hours 45 minutes. That's a deal.
Check out Bolt Bus, MVP Bus or Mega Bus