If you want local and a short trip, then visit either the New Hope & Ivyland Railroad (just across the state line in New Hope, PA) or the Black River & Western RR in Ringoes, NJ. Both will give you about an hour long trip. NH&I has a bit of a hill to climb, while Black River is kinda flat. I'm not sure if the steam at Phillipsburg, NJ is running at the moment or not.
If you're looking for a day-long trip, the best bet is the Reading & Northern Railroad, which is running some trips from North Reading, PA to Jim Thorpe during October on two weekends. There are very decent hills to climb in both directions, and a good lunchtime layover at the very touristy Jim Thorpe.
Good luck,
Kevin