Wrench on Angry's unholy Cor2rd/CorSquared (Corvette/Corvair) Challenge mash-up. Hell, come to my house and wrench on my Cougar with me.
When weather improves, take a slow drive around Belle Isle and tour the various facilities. If here through August, look in to the hydroplane races on the Detroit River.
Ice skate at Campus Martius Park downtown
Plenty of mentions of Henry Ford and Greenfield Village. Just wanted to add my vote for both as well. Henry Ford in inclement weather, Greenfield Village (outdoors) when it's nice. The massive steam locomotive and steam engines are AWESOME!
Detroit Institute of Arts (art museum) is world renowned. Awesome Diego Rivera mural and armor collection.
Shows/concerts at Fox Theater, Little Caesars Arena, St. Andrew's Hall, DIA (Sunday morning concerts), Fillmore, Cliff Bell's(good food too).
A wide variety of great restaurants are available in the city, both new and long-standing. Selden Standard, Slows (BBQ), London Chop House, Rattle Snake Club, Chartreuse, Green Dot Stables, Mexican Town (southwest Detroit), Republic, Mercury Burger Bar, etc. Sugar House is cool if you like craft cocktails.
AutoRama (hot rods, customs, rat rods) coming in March. Cobo Hall. Great show and BIG!
Bring your passport and go to Windsor, Canada. EZ in and out through the tunnel.
See the giant fist downtown Detroit and the former central train station (when going to Slows, Mexican Town, Mercury area)
If you're in to amusement parks, your not far from Cedar Pointe.
This years Hot Rod Power Tour ends at Norwalk Park on Friday June 14th.
The annual Woodward Dream Cruise is Saturday August 17th. Whole lot of car activities around that event including drag racing in Pontiac. For that matter, the M1 Concourse in Pontiac does some great C&C events and car shows starting once things defrost a bit. There are also other local cruises set up before and after the Woodward event like the Downriver Cruise, Gratiot Cruise, etc.
Plenty of casino action if that's your thing (also in Toledo and Windsor). Motor City had some design help from Chip Foose. It's cool to see from the outside at night.
Lot of local car shows once weather improves. Good Ford show at their Dearborn World HQ, GM has an employees show that's cool to see.
I hear the ACD Museum (Auburn, Cord, Duesenburg) in northern Indiana is cool. I have not been however.
Tour Indian Village area in Detroit then continue up Jefferson Ave along the river to see where the money was then where the money went in Detroit.
Tour the Pewabic Pottery in Detroit (near Indian Village).
GM used to have some cool cars at the Renaissance Center (GM HQ) in Detroit.
Speaking of Renaissance, MI has a good Festival (if you like that kinda thing) weekends August thru September.
That's all for now. I'll probably think of more soon though.