You can go to www.geocaching.org and type in the zip code. Where in MI are you looking for?
There is also the thread for cachers in the Midwest in the forums on geocaching.org http://forums.groundspeak.com/GC/index.php?s=c610ef991c89a9b8c5b7753277554ae1&showforum=18
Also, I know personally the founders of Michigan Geocaching Organization (MiGO). You can check out their site at www.mi-geocaching.org
Here's the list I found for Livonia using zip code 48150