As stated before, the Nn3 Yahoo group, is a great place as well. Just recently, we watched the birth, developement, and death of a Uintah 2-6-6-2T mallet. Republic Locomotive Works did a great job designing the kit, but in the end.... Marklin killed the project, and future plans for many of us. They have discontinued a great portion of the Z scale chassis used in Nn3, and are going to a limited-run style business with many locos. Without the Yahoo group, we never would have known any of this information.
Lastly, if you are serious about Nn3; get your hands on a copy of the Nn3 Handbook. You'll see it featured at nn3.org.