There are a number of Norfolk Southern Routes available for MSTS on Train-Sim.com.
Pocahontas Sub (this one is excellent and there are lots of activities available)
Atlanta & Macon (Atlanta to Macon, recently updated and has a few activities available, Inman Yard is nice).
Clinchfield Sub (Nice too. A few activities available)
East River District (Good one. Traffic is heavy in the activities)
Best part is they are free. There is some good equipment there too. MLT also has an excellent locomotive pack. There used to be a nice set available from KLW, but the owner took them off the site. It was used in the Pocahontas activities, but there is enough out there to replace it in the consists.
Broadway Limited Locomotive Works also has the Pennsylvania Middle Division available at http://www.home.earthlink.net/~bllw/.
If you want to order be patient. Sometimes it takes a long time to get a response, but they do respond. Has activites from Pennsy, Penn Central, Conrail, and Norfolk Southern. The version available here replaced, extended and updated an older freeware version.