This is a fun project especially for pre-schoolers. Take a piece of card (8 1/2 x 11) and cut out a shape. Christmas trees are a good shape for this time of year or make a butterfly (fold the paper in half to make both sides symmetrical before cutting.
Stick clear contact paper on the back and let the children tear up or cut small pieces of tissue paper and have them stick it on. When it's finished and hung in the window it looks like stained glass.