One of the easiest Halloween crafts around: lollipop ghosts. I've seen them hanging in the trees as decorations, and my kids usually get at least one in their candy buckets. If it's raining in your neighborhood, however, the tissue covering doesn't fare too well.
To weatherproof your lollipop ghosts, switch the tissue out for a square of white plastic cut from a garbage bag. Not waterproof but more durable than tissue: old, white handkerchiefs or pieces of cheesecloth.
Another last-minute decoration: citrus mini-Jack o'lanterns (cute in a lunchbox!).
Any more ideas for five-minute-or-less Halloween decorations?
More: Halloween hacks