We've already seen one option for a flat-packed Christmas tree, if you've got more holiday cheer than space to express it; the clever folks at Atypyk have taken it one step further with their House Christmas tree (poster) that goes up on the wall. Though the relationship to a real tree doesn't go much further than the tree-based paper it's printed on, the cheeky poster answers the question, "How many trees does it take to make this poster?" with "Less than it takes to make a tree!" if that backwards math makes any sense.
Though it's lighter on paper than a real one, this "tree" wouldn't be much fun to decorate, although it might make for some fun "Pin the angel on the tree"-type games. Get a blindfold and prepare for the festivities at ::Atypyk via ::Core77