Today I built a little cupboard into a nook behind a kitchen. It wasn't a very deep space (about 220mm) but the customer wanted somewhere to store their wine glasses with their cook books on top.
It's a simple construction out of low cost 18mm MDF.
I first built the base and added the sides and divider, these were notched to accept the top supporting timber that holds it together and provided much need support for the shelf on top.
Kitchen hinges were used for the doors making it flush when all the doors are shut.
Once painted I think this gives a very practical and low cost solution to utilising all the storage a space has to offer whilst still looking good.