Hey Gm
I've come into the thread late, so I'll just say my POV rather than comment on previous posts.
What follows is my opinion and I'm not claiming it as absolute fact.
I'm an atheist and definitly believe that 'worm food' is the only outcome of death. (Although organ donation is a nice idea

)
I don't know whether you can say some people value life more or less than other people, so I personally don't say that. There is a good essay that kind of relates to this called 'a religion guided missile' by Richard Dawkins, in which he makes the point that the sep 11 suicide attacks could only have been organised if you told people there was a afterlife awaiting them. (Not saying atheists can't be suicide bombers mind you, we can do anything we put our minds to, it's just a lot harder to convice us.)
My position on abortion is this:
1. Clearly individual sperm and egg cannot be counted as conscious, and therefore do not have the associated rights.
2. When the two combine into a zygote, it is hard to imagine that something smaller than a pinhead can have consciousness. (not a argument from incredulity, because there is no concievable way it can express consciousness)
3. A baby can be considered to have consciousness. (this is an assumption).
Clearly somewhere between 2 and 3 consciousness is obtained. Hopefully a nice, simple medical guideline can be obtained as to when this happens (brain waves, spinal chord development, etc.) but this may not be the case.
Assuming that a simple indiator of consciousness can be used:
(say for the sake of argument that it is 6 months).
Before this deadline the baby cannot be considered a person. Hence the parents are free to choose what to do.
After this deadline the baby must be considered a person, and any attempts to end it's life considered either murder or manslaughter.
(We had a incident in sydney where a 9 month pregnant woman in a car with her husband was rammed off the road and into a telegraph pole by a man in a 4wd who was upset at them going so slowly. The woman was pinned for a period of time and the unborn baby died. Technically she hadn't given birth yet so the man was only charged with manslaughter.)
A point that is often raised is 'Should victims of rape be allowed to abort?'. If there is a consciousness deadline (as I assumed before) then aborting before this is no problem. After this however would still be manslaughter. Hey I know they didn't ask for the baby, and they have had a crime commited against them but (if we hold that a baby is conscious) killing it does not make anything better.
If on the other hand no suitable indicator of consciousness can be found where we can draw the line, then any abortions should be considered manslaughter/murder. This may seem harsh, but the whole idea behind preventing conscious abortions is to stop innocent 'people' dying. We can't point to the actions of others (such as rapists or incompetent condom manufacturers) and say that because of them the killing is justified.
Note: Obviously if there is a either/or situation with the baby risking the mothers life then it should be allowed. No sense in them both dying if it's unsecessary.