Not really NW related, and I'm sure one of our helpful moderators will move this to the Travel&Dining forum, but I'll take a crack at it anyway since the post will remain after the thread moves.

What kind of food are you looking for? If nothing too fancy, take the light rail line to the Mall of America where you can either eat food court/fast food style or choose from a number of traditional sit down restaurants, as well as be protected from the elements (although the weather this week is actually quite mild ).

Otherwise, the de facto suggestion, IMO: take a cab to Fat Lorenzo's on the north side of the airport. 5-10 minute cab ride, tops, except if there is traffic. Italian/Pizza joint with many food options, plus you get Crayons to draw on the "tablecloth" with. They have a decent selection of bottled beers, but I forget what (if any) they have on tap.

If you want to stay in the airport, Ike's Food and Cocktails (intersection of E and C concourse, next to Rock Bottom) has some pretty good food and a quiet atmosphere, but it can get pricey. Avg. entrees probably run $15 and up, but you can get sandwiches or burgers for a little less.