This is a fun recipe I saw in a magazine (actually, their version was just covered with shrimp, but it gave me a lot of ideas!).
Basically you just purchase a styrofoam tree from a party or craft store (costs about $1.50), cover it with aluminum foil, and then use toothpicks to secure food items to it.
For the appetizer tree, I covered it with parsley (using toothpicks on the stems), then used vegetables that resembled ornaments (olives, cherry tomatoes) to place within the fake foliage. I set it on a platter and added cheese cubes, salami, and more veggies, and served it with several bowls of salad dressing for dipping (ranch, thousand island, and blue cheese).
For the dessert tree, I used fruit (sliced apples, maraschino cherries, strawberries, and grapes) and placed it on a platter. I purchased candy bark in white and dark chocolate (Whole Foods always has this) and placed it around the bottom of the tree. Then I placed heated bowls of caramel and chocolate sauce around the tree for dipping. Delicious!