http://www.vikinganswerlady.com/food.shtml is a fantastic resource. Also, http://www.ribevikingecenter.dk/en/explore/the-viking-kitchen.aspx is somewhat anachronistic, but they have a decent amount of recipes.

Now, to actually answer your question, the Northmen typically ate grains--primarily barley with some millet and wheat (and a few others). Porridge was a VERY common meal, although it wasn't necessarily the sweet stuff we're used to. Vegetables, meat, and dairy was often included. Bread was not commonly eaten--in fact, one particular figure was mockingly nicknamed for his love of bread and butter, a particularly "expensive" dish.

Meat was, well, not the most common thing on the Viking plate, and when it was, pork was more common than beef. Dairy was very regularly consumed and many meats and other foods were preserved by pickling in whey. Fish was likewise consumed where available (and it was usually fairly available). Pickling, fermentation, drying, and salting was all extremely common to keep fish from spoiling.

There is evidence of many types of fruit and vegetables used in the Northmen's kitchens. Apparently the pairing of fruit with meat was common--it still persists in Scandinavia today.

Beer was drank more often than mead, although both would be consumed as available. Wine was an expensive trade good and likely wouldn't be available to any but a particularly wealthy farmer or a leader.