My family took a tour to Door County when I was younger.  What I really remember of it was the Von Stiehl Winery in Algoma, WI.

I've had a few friends lately take the Leinenkugel's tour in Chippewa Falls, WI and from the pictures it looks like they enjoyed it.

You can also check out http://www.wistravel.com/attractions_in_wisconsin/

The "coolest" small town in America is Ely, as voted by Budget Travel mag.  It's a really fun place to visit, whatever the season.  Kinda has something for everyone.  You could do a circle tour, too, and go up the shore through Two Harbors, and then go north on hwy 1.  Return trip through either Tower (Beirut!) or Aurora (too bad the Whistling Bird isn't open any longer) or even Hibbing, depending on what you wanted to see.  Have fun, I love road trips!

I heard House on the Rock in Wisconsin is pretty cool. I believe it's close to Wisconsin Dells or Madison area. Wisconsin Dells, though touristy at this time of year, is quite a trip to visit as well.  
 
I also second the Door County area.

Drive through Door County, Wisconsin for a view of goats herding on grass rooftops.

You could try the Iron Range. There are several small towns right in a row for like 90 miles... but they're not your typical Anywhere, USA towns. There cool architecture, like in Duluth,  and lots of nifty main streets. The best part though is all of the open-pit mine overlooks.

I'd think you'd love taking a drive up the Keewenaw Penninsula of Michigan.  It is absolutely beautiful, remote and rugged.  There are some good roadside attractions along the way too.  Go all the way to the end at Copper Harbor, but don't forget a side trip into the once grand but largely abandoned town of Calumet, with some really cool architecture.  Another highlight is the town of Gay, which isn't really much of a town, but has the aptly named "Gay Bar" as its mainstay.  Go in, order a white russian and put some Elton John on the jukebox.  The locals will love you.  Finally, the beach and stunning coast by Bette de Gris is a nice place to cool off in the lake or get some sun.  Just my 2 cents worth...

I like Stillwater & Ashland.

Go west on Hwy 2 to Grand Rapids, (stop at the Forest History Center on the Mississippi) then north on Scenic Highway 38 to Marcel and Bigfork and Effie then east on Highway 1 and wind your way back through the range.  The Effie Bar is a must stop and the hike through the old growth pines in Scenic State Park (near Bigfork) is just amazing. While there check out the Antler Lodge and sit at the table under the moose to have a burger. If you really want to get wild check out the Lost 40, an area that was not mapped and therefore never got logged.  Then you will have really had a wilderness experience. There are 1007 lakes in Itasca County so take your kayak.

The UP is amazing.  We are sitting out a trip there this week with a group due to just having a baby but it has lots of fun little towns to explore all along it.

I second Stillwater, Bayfield and Madeline Island!  St Cloud too, it falls more in the "big city" catagory, but I love it there!

I am a relocated Yooper and my husband, kids and I rented a small cottage near the Porcupine Mtns for a couple days. It was right on Lake Superior and about a 15-20 minute drive from PM. If you are into hiking there are tons of trails and some are very long. 

Houghton/Hancock and the Keeweenaw are worth a trip as well.  In Houghton there is a local brewery, Keeweenaw Brewing Company
http://www.keweenawbrewing.com/

I recommend the Pick Axe Blonde Ale. 

Cool restaurant in Calumet 
Michigan House Cafe and Brew Pub
http://www.michiganhousecafe.com/

As a new Minnesotan I am looking forward to doing some of the MN road trips people have recommended.

I have to agree with Jude about the Antler Lodge. I've never seen more awe-inspiring taxidermy.

OK, I live here so of course I'm going to sound jilted.  Bayfield is swarmed with tourists and way overated.  Unless you're into going in and out of tourist traps/shoppes I don't know what people do here.  I will admit that the deck at the Bayfield Inn is the BEST spot to have a cocktail and watch the boats go in and out.  I was on the Island this past weekend and again, shoppes or drinking are the main activities.  Unless you bring or rent bikes and get all aerobic riding around the island.  

Now a drinking trip around the horn can be fun.  You can hit all of the little bars on your way (with a designated driver of course!).  Heading over from Duluth take the Highway 13 exit off of 2 and head through Port Wing, Herbster, Corny and then go south on C into Washburn.  Check out the most fabulous bakery in the world, Coco's and keep heading north into Bayfield.  Kind of a wagon trail right now through Red Cliff due to road construction but you can try your luck at the casino and then loop back to Corny.  Fabulous whitefish sliders at the Village Inn but be sure to sit in the bar and not the other side.  That's an annual for me.  

I also vote for the UP.  I love tooling around up there.  Did the Porkies over the July 4th weekend and was eaten alive by flies but love that place.  Go check out Iron Mountain and the fabulous Italian food there.  There are so many Forest Service campgrounds tucked into little lakes that you can't lose.

* I second the Porcupine Mountains. My favorite spot there is the Escarpment Trail at Lake of the Clouds.
* I also agree that the driftless region is charming. 
* And I agree the House on the Rock is "something to see"- a bizarre, hallucinatory counterpoint to whatever else you're doing on your trip. Half museum, half spook-house.