Bussard Ramjet (aka Interstellar Ramjet) :
Since you brought it up I'll start with this on this next section.
The Bussard Ramjet/Interstellar Ramjet would probably be one of the larger craft. Not quite as vast as a space elevator, but easily within size range of an MFD craft or Solar Sail craft. The biggest part of this ship would consist of a large Ramjet collector. Think of it as a giant funnel flying through space scooping up matter (namely hydrogen). What Bussard suggested was a type of projected magnetic scoop, that would extend far out ahead of the craft and push oncoming particles in like a funnel. This type of craft could also use a physical scoop to accomplish the same goal. Both of these comes with it's own problems. The magnetic scoop would need to be powered, and would probably use quite a bit of energy. The physical scoop could suffer damage of coul be destroyed completely by space debris. Each of these could be a problem for this type of craft, and where this type of craft would be used (interstellar space) this would be a huge problem since any rescue would pretty much be impossible. (tho an escape craft or altrnate thrust method would most likely be provided on such a craft) Anyway, this craft would collect hydrogen particles floating around between the stars to propell the ship by means of some type of fusion reaction.
Warp Drive (theoretical)
Well this one is a bit touchy, so i will have to come back to it at some point again, no one web page that i have found so far (i cant find the one i saw way back when just yet) can explain exactly what is going on, but here's a basic explaination that i picked up.
What warp drive is (atleast my basic understanding w/o finding what i've been looking for) is that since nothing in space-time can go faster than light, if you were to remove the ship from that space-time and place it in its OWN small bubble of space-time, you could then move that bubble of space-time around inside the larger space-time faster than light. You would fold space-time around you (using large amounts of energy) then force that bubble either by shape of the bubble (by pinching one end and oozing your way throught eh fabric of space-time) or by shifting different energy levels of areas of the bubble (maybe projcting mor energy toward the front or back o the bubble, pushing the bubble forward in real space-time). When you are traveling at warp speed your ship isnt really moving at all (though it could be, however that movement would be insignifigant in comparison to the super speeds of warp speed that they wouldnt add anything really to your speed. For expample what use would traveling at 1000mph be when you're rocketing forward at 5x the speedof light already)), you're sitting in a bubble of your own space, and that bubble is what is moving. You would tear your way though the fabric of spacetime, (hopefully) sealing it behind you.
It would be like an ant sitting in an air bubble at the bottom of a pool, then that air bubble disconnecting from the bottom of the pool and rocketing up toward the surface.
When i find more info i'll try and slap it up here, but here's lots of ways to look at warp drive. This is just one explaination (and a rather crappy one)
Will we be able to do something like this in the future? Maybe, but with the seemingly insane amount of energy needed to fold space-time, it would be pretty tough. So far the only thing that may even come close to this type of idea in any way whatsoever would be the MFD.
I'm pretty tired now trying to explain that (and i haven't slept in like 20 hours), so I'm gonna take another break LOL. Later I'd like to get more into fusion and fission propulsion. I'll also touch on other things that are not-so-up-coming like wormholes, and other stuff like Tachyons. This is where my understandings start to break down, so explaining what i know/will find out will be pretty fucking tough... ... but then again i have nothing else to do.
