XtrkCad is a fine open source track planning software package that runs on Windows, Linux, and Mac. See
http://www.xtrkcad.org/Wikka/HomePage for details. Volunteers maintain the software and continuously update the libraries. As a result, the libraries are current for almost all makes of track. The learning curve can be on the steep side - be prepared to do the tutorials to learn the software. There is a Yahoo users group for questions, advice, and updated libraries.
