Here is an illusion that's both effective and practical, that you can perform with 
Folded it will fit into the trunk of an ordinary car, but unfolded on the stage it looks incredible and can be a nice finishing touch to your show. 

On the stage stands a solid metal pole with 3 big rings fastened to the bottom. Your assistant steps inside the rings. Then you trap her inside with 7 additional rings. You cover her with a cloth and then just a moment after make it fall back to the ground - the assistant is now standing outside the rings!

The effect can also be performed the other way around by first having the stand outside the rings and then making her appear inside! In the youtube video above you can see how Arsene Lupin performed the illusion on French television.