I'm taking my 17-year old niece to look at colleges (Grinnell and Carleton) this week, and would love some chow recs for: (1) a place to grab a quick bite late afternoon by the airport in Des Moines; (2) places in Grinnell for 3-4 meals (alternatively, a dinner place in Marshalltown or Newton); (3) an option for a quick Saturday lunch along I-80 (between Grinnell and Des Moines) or I-35 (between Des Moines and Northfield, Minn); and (4) Saturday dinner (possibly on the late side) and Sunday breakfast restaurants in downtown Minneapolis (near the Westin). We're looking generally for places that we can go in jeans or relatively casual clothes and would like to stay in the under-$20 per entree range. Any type of food is fine.
For breakfast Sunday AM you can't beat Hell's Kitchen but you'll have a hard time getting in. There was another post recently about someone touring Mpls colleges. http://www.chowhound.com/topics/443427 Check that out. Sorry but I can't really recommend anything between here and Des Moines. I've done the drive many times but no idea where to stop. Likewise with Northfield.
I will second Hell's Kitchen. It is about 5 blocks south between Nicollet or Marquette on 10th I believe. But unless you show up very early, be prepared to have a little wait (it is worth it). I recommend the sausage bread, ricotta pancakes, and/or buffalo bennedict with mango/jalapeno hollandaise. Great coffee.
Saturday dinner under $20 per entree downtown isn't terribly difficult, though there may be more interesting areas to hit-up within a quick drive or cab ride (Eat Street, Nordeast, Uptown, Seward, Midtown). Do you have a cuisine preference (comparatively exotic vs traditional)?
You didn't specifically say you were looking for a place to eat in Northfield, but in case you are I would recommend the Ole Store Cafe for breakfast or lunch (http://www.olestore.com/) and Chapati for dinner if you like Indian food. (http://www.chapati.us/)
I agree with the people recommending Hell's Kitchen in downtown Minneapolis for breakfast: it's really good food, but the wait for a table will be around an hour.
If you're looking for something easy, Ike's Food & Cocktails is just one block north of the Westin. I don't know if I would classify it as a real "Chowhound" kind of place, but the food has been consistently good each time I've been there, with generous portions too. And let's face it, sometimes you just want a place that's close to your hotel.
1001 Division St S, Northfield, MN 55057
Ike's Food & Cocktails
50 South Sixth Street, Minneapolis, MN 55402
If you need to stay near the airport, I'd go with Skip's. It's at 4000 Fleur, just a few blocks North of the airport, on the West side of the street. Kinda pushed back.
Another choice a bit farther, Orlando's for good pizza and sandwiches. On Park. Just take McKinley,it's the first street North of the airport, West. It winds around to 42nd, 42nd stops at Park. Orlando's is about a block West.
The Grinnell students dine in a funky old building that, I believe, used to be a church. That'd be a good way to check out the campus meals. Quite a spread, as I recall. Also try the train station southeast of downtown. It's been converted into an upscale restaurant, but I don't remember the name.