i downloaded the demo of Railroads! earlier and remembered how much fun i had with these simulation type games (simcity and rollercoaster tycoon in particular). i heard that RT2 was the best of the series.
Yes, TTD FTW. I never realized there was a cult following for this game. openTTD is your source. To install openTTD you need a copy of the orginal game. Go to the forum (or follow a link in the the openTTD d/l area) and find a free win9x version of TTD. It's not illegal i believe because it seems nobody claim ownership to the original game anymore. You can d/l all the cool graphic mods then. There's also a 32bit graphic version in development right now by the openTTD team but it's not directly in their website right now.