Username or EmailPassword
I may be antidiluvian, but I still use troff (or groff in its OSS form). It sets very, very nice type, and its preprocessors are extremely powerful. I use them all, pretty much -- tbl, eqn, pic, refer, grap and chem. You can include images in .eps format.
It is much like TeX in that it uses an ascii input file, separates text input from formatting, and is a complete typesetting language. The macro packages make it pretty easy to use, and it is already installed on most every BSD, Linux and Unix system. It integrates nicely into Unix through the man pages. And yes, there is still active development going on.
One is also part of Unix history, as troff was the vehicle used to justify development of Unix within Bell Labs in the first place.