Hello marygfaile,
One that I like is "Central Valley V1" by the creator leeferr. It has nice industries, including steel mills, but it is very heavy on the computer unless you have a very strong one. (Or don't put in all the scenery)...
Leeferr also has a simpler "Matlin Hump Yard Revised" and an even simpler "Matlin Hump Yard". These will be under 2004, not 2006 ...but I'll bet money that they will work in 2006!
So that's a few I know of... PS, you have to learn somewhere about how to use that "hump yard" feature (of letting the cars roll into each other). I have used it, but I do it in a simplistic way, (probably wrong) but you do not have to use that feature...
Good luck! Bob P.
Also, Leeferr has a "session" for " Matlin Hump Yard Revised" (look up his username in Sessions, and 2004. But you have to download a pile of rolling stock!) Bye!