Tomato cage ghost. Seems easy enough.
Melted crayon pumpkins- nice alternative to cutting a jack-o-lantern
25 DIY Halloween Decorating Tips for the Home, but you could use them in your business as well!
Halloween Door Art - no instructions, but easily enough duplicated using tin cans
Anythingology: Halloween door
What a great way to give a special trick or treat to neighbor kids. And a great idea for a classroom party.