Indianarailroads.org is regional as the name implies, but there is a ton of useful info there and a whole lot of extremely knowledgeable folks both in and out of the railroad industry. Click on "Bull Session" for the forum. Be warned, they can get a little crusty sometimes, so if you post a question and they dump on you a bit, just grow some skin and don't take it too personally. Lots of nice folks on there too.