There aren't many trail runs in Michigan especially long distance (ulta) runs. If you're into that kind of thing check out this web site: www.runwoodstock.com I've run races by this sponsor on this course before and they are well hosted runs. A hilly course for Michigan.
I've always been bit of a Hippy wantabe and I find the "Woodstock" marketing appealing.
So, load up the mini van, get the 8 track tapes, grab a frisbee, roll up a fat one (sleeping bag, it could be cold camping ;-) and join me. It'l be groovy, man.