There are a number of options in a variety of prices including free. Here are a number of links (hope they work???) I found Googling:

3rd Plan It $125: http://www.trackplanning.com

Cadrail 8 $60: http://www.sandiasoftware.com

3D Railroad COncept and Design $50: http://www.theliquidateher.com

Templot Software $85: http://www.templot.com

WinRail $75: http://www.winrail.com

Sillub Technology $FREE: http://www.sillub.com
I do not have any working experience with any of these programs. Although the highest price, the 3rd Plan It software sure looks good and you can operate trains on your designed layout.

__________________
Bruce (McToots) McElhoe
KAMRI President
and Web Site Moderator