slides and documents

I wonder if anyone has experimented with coding documents in such a way 
that slide presentations can be extracted from them?  In other words, 
my (academic) documents are almost all of the basic structure:

intro
literature
case study
conclusion

There might be a second-order sectioning within that as well, but that 
itself can only form the skeleton of a presentation.  Any suggestions 
on how to code a document such that it can be virtually completely 
built directly from the document (as opposed to a separate "slides" 
file or whatever)?  Maybe have "invisible" sections" somehow?

Bruce