When we need a box (which isn't that often as most of our items go as letters), we use a wine box from the local bottle shop, which we cut down to size.

Obviously this wouldn't be an option for larger items, but works well for us.

We also find that the cardboard is good for using as stiffening in our larger envelopes.

We don't use a lot of bubble wrap, but we do have a new roll on hand at all times.

We also find old phone book pages useful for filling the spaces in our boxes.