Hidden doors and secret passageways by Creative Home Engineering, Gilbert, AZ. (Click on photo for larger image.) Photo found here: http://hiddenpassageway.com/ Hidden Doors Bookcases, Houses Ideas, Offices Doors, Secret Passageway, Secret Doors, Hidden Rooms, Secret Rooms, Hiddenpassageway Com Ideas, Books Cases
Hidden doors -- This company makes doors, bookshelves and anything you can think of that fits your existing doorjambs thus hiding the door (and also making use of the space). If you click through checkout the "gun cabinet" door. Lots of great ideas.
Secret passageway! Cute idea if your house is designed properly. I remember a family friend's house had a hidden play room under their stairs. To get in, we crawled through a little door in their coat closet. Way fun for kids!