SMOC – Orienteering meets in the metro D (and Yankee Springs by Grand Rapids).  SMOC has three permanent courses for year-round training

Lost Arrow Sports – Produces a variety of high-quality navigation races in the southeast Michigan area, from short to long rogaines, paddle navigation, and adventure races

Michigan Adventure Racing – Adventure Races with and without Amazing Race-style challenges in the Grand Rapids area

Attackpoint – Training log and Orienteering / Adventure Racing forum.  Includes groups for SMOC and Michigan AR training

NSF Adventures – Nav races on big hills in Ohio