Getting back to your questions cyberice:
Teleportation
The others have already sufficiently answered your question about teleportation. Demolecularization (if that's a word) isn't the answer. Unfortunately the problem with reconstructing a copy of the original subject, or matter-energy-matter conversion, is that you need to know a considerable amount about every particle in the original subject. This is where it gets tricky: due to something called quantum uncertainty, predicted by quantum mechanics, you can never know everything about a particle. For example, the more you know about its position, the less you can know about its velocity. This has to do with the unavoidable interference caused by observation. And unless you know exactly how fast a particle is moving, and exactly where it is when you take this observation, building the duplicate or reconstructing the original in the matter-energy-matter conversion, is impossible. Then there's also the core of quantum mechanics itself: everything is probability. Even if you could know completely both the position and velocity of a particle, you can only determine the probability of where it will be in a few seconds. You can never know for sure. Now I seem to recall reading somewhere that a single photon had been "teleported" and that the information was gained through a process called entanglement. Photon A is the one you want to teleport. Photon B is in the place where you want to teleport it to. Now we introduce Photon C which is entangled with photon A. Photon A is destroyed in the process and photon C now contains all the information about it. Somehow the information contained in photon C is then transferred to photon B, which becomes a duplicate of photon A. The point is, even if teleportation ever is possible, it will no matter what require the destruction of the original.
Time travel
According to Einstein's theory of Special Relativity, as you increase your speed relative to another observer, that observer will note time as passing more slowly for you than for them. There is an extremely good article at
http://science.howstuffworks.com/relativity.htm that explains why this happens and does so in very easy to understand, non mathematical terms, if you would like to know more about it. Once you accept time dilation as it's called (which actually refers to what the moving observer sees), then you can see how it can be used to "travel" to the future. If you were to blast off in a spaceship and accelerate to 0.9999999999999 the speed of light, for every 1 second that passes for you, about 2236068 seconds would pass for everyone back on Earth (to anyone who knows how to use the Lorentz equations, yes I did calculate this, Cyberice asked for the math to be left out). If you maintained this speed for 24 hours, over 6,000 years would pass back on earth. You could then return to Earth having hardly aged but millenia after you left, effectively "travelling" to the future. Unfortunately, reaching such fantastic speeds is no easy task. Another relativistic effect is that as you increase your mass, more and more energy is required to accelerate. This number becomes infinite at the speed of light (the Universe imposes many contraints making accelerating to the speed of light impossible). Particles in atom smashers are accelerated to speeds comparative to the one I mentioned, but accelerated a spaceship to that speed would be quite a feat indeed. Still, it's possible. Time travel to the past is a different matter. It's not simply a matter of traveling faster than light (not only is this impossible, but plugging such a value into Einstein's equation yield's an imaginary number, as opposed to the negative number that would suggest time reversal). There are possibilities though. There are objects called cosmic strings, their existence is purely theoretical but if they do exist they are highly concentrated strings of energy, remnants of the Big Bang, that are thinner than a nucleus of an atom but several million kilometres long. Two of these strings circling each other would warp spacetime (now we're dealing with Einstein's Theory of General Relativity) so significantly, that spaceship flying around them could theoretically arrive back at it's starting point before it even left! Again, the existence of these strings is purely mathematical. Still, it is possible. Special relativity says that events that are simultaneous in one reference frame aren't necessarily simultaneous in another (see the article I mentioned). That means one observer could see an event happen and it's in their past, while it has yet to happen for another observer, it's in their future. This suggests that what we call the past and future are forever frozen in spacetime and the present is just our fleeting impression of the Universe as it is as we hurdle through time. If that's the case, the past and future are always there, always part of the Universe, and it's only accessing them that's the question. Perhaps the methods I suggested are the ways of going about this.
Teleportation and time travel are definitely on the cutting edge of physics. They may slowly move from the realm of science fiction to solid science, or they may remain idle fantasies of the human mind. Time will tell.
Hope that helps!
