This ghost-cloche is incredibly quick and simple, if you already have a nice glass item like Chic on a Shoestring's. (The filling inside the glass is fluffed-up pillow stuffing!) If you don't, you can DIY one with a 2-liter soda bottle; cut off the bottom portion, and cover the cap part with clay. Here's a trickier, but more professional-looking, way to make one, from Our Peaceful Planet: soda-bottle cloche.
The ultimate in ghostitude: An empty, see-through fabric form that appears to be holding itself up by supernatural means (a.k.a. spray starch). Allow me to present my favorite spectral project, The cheesecloth ghost. There are many to be found, but I like Every Day is a Crafting Day's shape the best. Bravo.
Of course, I like this miniature version very much, too. I love the idea of a little terrarium for a tiny pet ghost. The spirit itself is made much like the large version above, but has a hidden base that attach to the inside of the jar's lid. Go to Landee See Landee Do to find out how to capture your very own ghost in a jar.