I had picked up a bundle of window branches at a garage sale for 50 cents. The kids painted them orange and black. We stuck them in vases that we already had, filled with black and orange strips of construction paper. We made ghosts out of tissues and hung them with dental floss. Joe even added some "dental floss spider webs" to his, which was cute.
This whole project only involved the cost of the willow branches as we had everything else on hand. We've moved them to the buffet as Amy kept bothering them by climbing onto the table and I must say that it puts a little extra "Fall" into the air!