The Stock Panel can be accessed via the small button on the left, under the date display. It lists every single item in-game and sorts them into seven categories, and within each category the items are sorted in alphabetical order. You can see how many of each item you have by looking at the number below the item's icon.
Raw Food is listed here, including raw meats, eggs, milk, wheat and flour. Raw food barrels also lie here.
Prepared Food is listed here, including cooked meats, baked items and fruit.
All types of Weapons are listed here including melee, range and magic weapons.
All types of Armor are listed here: from wooden helmets to fire breastplates.