Yes we are on time but this is yesterdays train
For locos and rolling stock, tons.
As far as routes there are a bunch. What I can remember right now:
The Arkansas and Missouri is a payware add-on which models the regional by the same name with an all Alco fleet.
The Western Maryland Scenic is freeware.
As is the San Diego & Arizona.
The San Juaquin Valley Railroad is present in the payware Tehachapi route by 3dtrainstuff, including some activities for it.
Cargill's GP9 is in the Cajon Pass payware route.
There are also a bunch of fictional routes which model regional action. Ohio Rails is a freeware route that has 2 competing regionals.
The Canton Family of add-ons is really good too. The activities included give you the feel of working for a short line. You learn the route a little at a time. Lots of running and switching. It is worth the cost. The Ohio rails freeware route is the predecesor to this route. The A&O sub (Arkansas and Missouri) gives you the same feel as you learn the route by running trains. Metro East is good freeware for the feel of a commuter line.
I know there is a list of routes available on train-sim, both pay and free with a description of the routes. It has not been updated in a while, so a bunch of the newer releases will be missing. I think it had close to 200 US routes on it the last time.
The best place to find routes would be in the file library at train-sim.com.
Wisconsin Locomotive Works is working on a freeware shortline route of the WSOR (Wisconsin Southern) from Janesville/Milton, WI, to Waukesha, WI. The website is http://www.geocities.com/trainsim1/WLWProjects_route.html. More information will be coming soon.
YYYYYYYYYYaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaayyyyyyyyyyyyyyy, my favorite railroad!! (I think I overreacted there a little.