Tom created files in the LDraw format and full instruction sets in HTML and PDF for the variety of motive power and rolling stock he designed and has displayed at L Gauge (Tom’s LEGO® Stop). Also check out his DCC conversion information.
Bob offers the multi-part file depicting the construction of his GG1 and pictorial instructions to build an F40PH locomotive in Amtrak livery at Brickshelf.
Constantine has a page at his personal website with links to files in the LDraw format for vehicles, buildings, and trains, including the Kawasaki Bi-Level car, the Norfolk Southern Top Gon car, and the WMATA Metrorail cars originally designed by Kevin Loch.
Nate designed a gondola and posted a file in the LDraw format to Brickshelf.
Michael posted pictorial instructions to build a GG1 out of the parts in 10183 Hobby Train to Brickshelf.