To perform this trick requires 3 items:
-A black stocking
-A small piece of adhesive clay or a small piece of transparent tape (scotch tape)
-A playing card
First you must prep the stocking. What you do is cut a length of stocking along the 'grain'. If you look at the end of the strip of the stocking you can see that the strip contains very small strands. You have to free one of those strands. The fact that the strand is black means that it absorbs light and thus is nearly invisible.
Now you tape or use the adhesive clay to attach the strand to the back of your ear. Tape or stick the other end to the middle of the card (on the back of the card in the dead center...the card should be dead centered so that when dangled it will be completely level). At this point you can perform your trick.
You can also be a little more innovative and instead of attaching the end of the strand directly to the card, attach it to..say..your belt buckle using the clay. Then you can ask an observer to provide you with any item or a playing card. Use some slight of hand (diversion) to pull attention away, and remove the end of the strand from your belt and attach it to the card or object. Now you can add some effect and make it float, orbit, or levitate. Before you hand the object back to the observer, remove the adhesive clay (and thus the strand) so they can inspect it.
MAGIC!
EDIT: This is a common trick. If a magician gets mad that I posted this, they need to do a simple Google search. You can buy levitation kits at any mom and pop Magic shop. The kits include the above stuff along with a video or instruction of sort. In this age of information, we can't expect things like this to stay a secret. I think this is great though. It forces magicians and performers to actually come up with something new and innovative.