[shushcat]

As other commenters have mentioned, Pandoc[1] is an incredibly useful tool for converting documents between formats. I do not, however, think that its usefulness in a solution to your specific problem has been framed clearly enough. It uses a version of the markdown syntax which is slightly-modified to ease writing of lengthier or academic documents. For example, a citation to a BibTeX bibiliography (usually performed in LaTeX by typing `\cite{McElroy-2000}`) is written `@McElroy-2000`, headers can be tagged to simplify internal references, and actual LaTeX commands can be called if you need them. Since the changes from standard markdown are minimal, you can write using any of the many markdown editors which are available.

As to my particular setup, I write Pandoc markdown in Vim using a plugin which I wrote for that purpose.[2] Nothing fancy, mind you, just light syntax highlighting, some keyboard shortcuts for (1) exporting to html or pdf (via-LaTeX) and (2) jumping between headers, and document folding, the latter of which is especially useful for outlining and organizing lengthy documents.

[1]: http://johnmacfarlane.net/pandoc/

[2]: https://github.com/shushcat/minimd