The MTA runs old subway train cars on the V line on Sundays in December. I was on the trains in 2008 and I know they did it again in 2009. I hope they continue to do it. Check the MTA site in late November.
If you like old-time subway stuff, ride the 6 train past the last stop downtown. You’re “supposed” to get off the train at City Hall, but try to stay on it to go through the loop around. There’s an old, closed station in the loop around, and it’s quite pretty. You can probably search You Tube for some clips people have posted of the ride.