Clubs/Organizations:

National Model Railroad Association
Dakota Southeastern Division of the NMRA
Sioux Valley Model Engineers Society - Sioux Falls, SD
Missouri Valley Model Railroad Club - Yankton, SD

Real Railroads:

Burlington Northern Santa Fe
Rapid City, Pierre & Eastern The former DME

Manufacturers:

Athearn
Bachmann Industries
Digitrax - Producer of the Empire Builder II system that we use on our HO layout
Kato USA
Walthers

Magazines:

Model Railroad Hobbyist - a Free online magazine
Model Railroader Magazine
World's Greatest Hobby - Your Guide to the World of Model Trains!