If you happen to be looking for a cemetery in Michigan, and you do not know where it might be, here is a book that might help you: Michigan Cemetery Atlas (Lansing, Michigan, 1991). This book lists the names of cemeteries in Michigan, and gives a location for those cemeteries by county. This is one way a person might be able to determine where a cemetery is located, or if they do not know the name of the cemetery, looking at the map for the county might help a person narrow down the name of the cemetery he or she is looking for. I know that the Library of Michigan has at least one copy of this book in their genealogy section.
Another source one could use to locate the county of a cemetery is the Library of Michigan Michigan Cemetery Sources database on its website. Again, this is a website that will give a list of names of cemeteries in a particular location. It does not contain a map of where the cemeteries are located, and the burial records for the cemeteries are not online. This site, though, is a place to start, if you are looking for the names of cemeteries in a particular area.
Of course, if you are going to go visit one of the cemeteries in Michigan, I would obtain a map of the local county that you plan to visit, so that you are able to find the cemetery. In addition, paying a visit to the local library near the cemetery would be a good idea, especially if you are looking for a specific person buried in that cemetery. The local library might have a transcription of the tombstones in the cemetery, and finding out where a grave is located will save time when you visit the cemetery.