Take a look at Dave Marshall's web site at
http://www.railfanswelcome.com . He has a list of frequencies by state and a list of railfan locations.
You could always hook a scanner up to a computer and record the audio. Then play it back as an mp3 or wav file. I've also seen guys using FRS radios (or 49Mhz HTs) and simulating traffic between a dispatcher and train crew as well.
Or, just move the scanner into your train room and listen as you operate your trains. I've done that before while operating MSTS routes for my local area.
Warren