If you're hunting morels, you know that the first rule of putting dots on a map to say where you found them is to be imprecise. It's OK to say which county you located the morels in, but don't narrow it down any more than that. I happen to know that morels can be found in Marquette County, but even my mom won't always provide an exact location.
With this mapping in mind, here's a few sources for early morel sightings in Michigan.
The Facebook group Michigan Morels has daily reports with photos of people showing off the results of their hunt. No maps, but lots of county reports.
MorelHunters.com ("Where the hunters gather") has a morel progression map on their front page. The Michigan bit of it is included below, as of 1 May 2013.
A similar map is the Morel Mushroom Progression Sightings Map from MorelMushroomHunting.com. I've cropped it a little wider to show the progression from south to north.
Mushrooms are known to frequent burn sites, popping up the next few years on the burnt over location. Two sets of maps from previous Vacuum posts are useful here, with the caveat that you should check with land owners before hunting morels in the wild.
Sleeper Lake Fire, Luce County Michigan, a 2007 fire; the account of the 2008 morel season said a "once in a lifetime" opportunity for picking.
Duck Lake Fire, Luce County Michigan, a 2012 fire. You'll be hunting for mushrooms in the Tahquamenon woods.
Some news stories from this season, via a Twitter search for Michigan morel:
A beginner's guide to morel hunting in Michigan, Lansing State Journal.
Northern Michigan mushroom outlook: will the cold spring freeze out morels? Petoskey News
Hunting for morel mushrooms? Here are some tips, Detroit Free Press