Storage space is one of those things that few houses ever seem to have enough of. If you need to add some extra storage to a room, forum user mairanellis suggests building some shelves onto the inside of the wardrobe door.
All you need is a few simple wooden boards from a hardware store, and maybe a little paint if you want them to look nice. Other than that, it's just a matter of nailing everything together. You'll want to make sure you build in some guardrails on the shelves to ensure things don't slide off. Hit the link to read more.
Closet storage [Ana White]