A disappearing act was my first special effect. I did it with a Hi8 camera at the age of 15 and without the aid of a computer.
1. Put your camera on a tripod.
2. Stop recording right at the moment you want your actor to disappear (I did it when he took a step, so the motion would help sell the effect).
3. Move your actor from the shot, and record a few seconds of an empty scene.
When you play it back, your character convincingly vanishes.
And, in many ways, that's exactly what was used for this simple yet effective special effect:
Now You See Him
Now You Don't
The beauty of this shot is that while the effect involved a computer program slightly more advanced than iMovie/Windows Movie Maker, it could be reproduced on software that costs under $100. And if all you happen to have is Windows Movie Make or iMovie, you could do something almost as effective with the three steps I outlined above and a couple of friends who are willing to walk through your frame.
Be inspired! There are many simple effective special effects that you can do, right now, with the equipment you have.
Your Media Production Mentor