What tools do you use to write papers?
From the little experience that I have, theoreticians spend a large amount of time writing and refining papers, besides actually being creative. That is, communicating their work to other people. Maybe papers are not the right way to do so, but that should be left for another discussion. In any case, it seems like one wants to reduce the time spent writing up the results by using as good software tools as possible. So, this questions aims at finding out about some hidden treasures out there.
I think most of us use LaTeX and some system for organizing paper references. But there are also vim/emacs and some very nifty libraries which have been a huge time saver for me. Therefore I wanted to know about the setup you use for writing papers, and maybe also some things you've tried to learn and didn't work for you. I would be especially interested in things which might not be as well known but have turned out to speed up things, even if it is, say, some very specific software for drawing graphs or auto-completion features.
Don Knuth tells about his setup in an interview here. Search for the question "What set of tools do you use [...]".
UPDATE: Sadeq pointed me to a discussion about tools for drawing diagrams here.