It doesn't have to be just bread slices, you can do this with biscuits, english muffins, bagels, etc.
Toss cubes into a ziptop freezer bag and store in the freezer until you have a full bag or enough for whatever you need to use them for.
One of my favorite uses for homemade bread cubes is for my Thanksgiving Sausage Stuffing. But this stuffing is so good, you don't need to wait until the holidays to enjoy it. You can also make your own Seasoned Dry Bread crumbs instead buying them at the store. This will save you money as well as give you the control to flavor them as you like.