My co-worker Asta made these wonderful ghosts for the nursing home last year. She placed them on the patio and they could be seen by the residents from the dining room and the main dayroom. They stayed out in all weathers for a few weeks and made a great addition to our Halloween display.
What you need for each ghost:
A large ball
A solid stick 2-3 feet long
Black and red paint and a brush
Safety pins or a stapler and a chair for your ghost to sit on
Tape the upper end of the stick to the ball by winding the tape several times around both, and then attach it securely to the back of the chair (with tape or string).
Paint ghostly eyes and mouths on the white sheets (loosely drape the sheets over the ball to gage where to put the eyes before you start painting).
Drape the sheet over the balls as you can see in the picture and use safety pins or stapler to fix the sides of the sheet into place.