Sorry to have missed this post!
I work in Essen and live in Langenfeld. The AMC Langenfeld holds the premier indoor offroad race series called the Sixdays, which always pulls a crowd. A couple of the Belgian and Dutch drivers usually make it over and a good time is had by all
If you are here in the summer we also have a fairly kick-ass astroturf track outdoors. There is a thread down in the german section covering the 2010 german champs which were held on that track. If you refer dirt there is a club in Duisburg and one in Dortmund but they don't run over the winter.
I would love to have the dude with the hat at one of our race meets
Give me a heads-up when you get here!