TreeHugger has shown many ways to hide the bed; most are designed to gain more space. But the Red Nest by Paul Coudamay doesn't; the bed is still there taking up space, but is hidden by the sliding bookcase.
Built in idea for the dining room door! Oh how I love built ins. Ikea Shelves Into Built-in Bookcases :: I really love this. You could turn any room into a library with this idea. And you don't need ikea for it, either.