actually, i have a theory on that. .....ready?
you know how people claim to be floating down a tunnel of light and seeing all images of people and places.... well, i believe that the brain is like a large capacitor, storing electronic energy. as a person dies, the brain reacts and expends electronic energy, thereby giving one the sensation of floating down a tunnel. the tunnel they are experiencing is the brain shutting down certain parts, trying to save energy. memories, images, etc are now quickly being expelled in an attempt by the brain to "self preserve" itself.
so, basically, the images are just the brain losing or expelling energy, the "tunnel" is just the brain shutting down unneeded areas of itself, thus blocking off other areas of it...giving a tunnel effect.
so, to answer your question, i believe we simply die and that's that.....like any other living organism on earth.
This, only it's part right. The energy doesn't just go "poof", it changes into some other form of life. Remember, energy is never created nor destroyed, only changed.