I could get lost in this map for hours:
Although not a track, try searching for 'abandoned', 'derelict', 'sunk', 'buried', 'beached', etc. on this map:
The second website you found really impressed me. And I found some really cool steam engines:
Two rusting large engines in the middle of nowhere in Maine in fall
BEDT #16 in Long Island. What is the kind of this locomotive?