Here's an awesome experiment you can try if you're looking for a last minute way to decorate your cubicle or house for Halloween. It's particularly great if you have one of those tiny relaxing waterfalls at your disposal, since replacing the water with cascading smoke is sure to have everyone thinking you're some kind of wizard -- despite your costume.
All you need to do is roll a sticky note into a tube slightly thinner than a pencil, and then light one end. The smoke will magically pour from the other end of the tube, cascading over rocks or other decor -- but it's not magic. Smoke is usually carried skyward by the heat of a fire, but in this case it has a chance to cool as it travels down the sticky note tube, becoming heavier than air and sinking as it escapes out the other end. So your party guests will learn some fun science in the process. Besides, it's easily better decor than the pile of dirty laundry in the living room you claim is haunted.