When I have good but stale bread, I make bread pudding.

Bread pudding can be sweet or savory and it is very flexible. It can be fancy with expensive ingredients, but I mostly use inexpensive leftovers and its pretty fail proof.

The basic recipe is torn or cubed stale bread, the drier the better, milk, and eggs. You can add fruit and sugar to make a dessert or breakfast, and a simple glaze or sauce to make it fancy. Here is a sweet recipe to get you started. When made ahead of time I find this makes a nice, quick breakfast, hot or cold. I can just cut a square and go.:

Cut or tear a loaf of stale bread into squares, about two inches, more or less, in size. Let them sit and dry even more if you want, then put them in a buttered 8x8 baking pan. In a bowl, mix 4 eggs with 2 cups milk, and sugar ( depends on how sweet you want it, 1 cup will make it dessert-sweet. I use 1/2 cup for a breakfast pudding). Mix in cinnamon, and a chopped apple, and pour it over the bread cubes. Let it sit until the mix has soaked into the bread a bit, maybe 15 min. I'll smoosh the bread into the egg mixture too. Bake at 350 for 45 min, or until the center is not goopy. I like it firm, so I'll often let it bake a bit longer.

Eat it hot and puffy with whipped cream, or cold with fruit and yogurt.

Savory bread pudding is also great. Use heartier bread, like seeded whole wheat bread, skip the sugar and add shredded cheese, leftover protein, and veggies, salt and pepper. Serve hot sprinkled with cheese or salsa and a salad, (or whatever sounds good), or cold as a quick all-in-one lunch.

I find that sweet bread pudding is nicer with whiter, or lighter bread, and savory is nice with either light or hearty whole grain breads. Bread pudding lasts about 5 days in the fridge, and reheats well, but it's not good to freeze. It changes the texture.