This project is easy and inexpensive and certainly one in which the kids can help. We took a thrift-store frame, wrapped the inside with yarn and cotton to make it look like a spider web. Then spiders and a "Welcome" message were hung within the webbing.
black paint and a paintbrush
large wood frame
small wire nails
4 to 8 felt furniture pads
small toy spiders
white cotton spider webbing
yellow or orange yarn
picture hanging kit if not already attached to frame
On the back of the frame, along the edge, hammer in the small wire nails. Insert the nails so only about a 1/4" is sticking out of the frame.
Place the felt pads on the back of the frame along the corners so the nails will not scratch the house or door.