LaTeX, ConTeXt and plain are the most well known TeX formats/macro packages. But there are others, such as Lollipop. What others are out there and are any in use these days anymore?
Less known formats
A search in the TeX Live 2009 tree reveals:
Arthur Ogawa is well known for his work on TeX and LaTeX: he is the current maintainer of the RevTeX class, for example. Formats 1, 2 and 4 were directed to physicists, only TeXsis was, as far as I know, rather extensively used.
StarTeX had a quite interesting approach, as its syntax is HTML-like:
Technically not a format rather a macro package built on top of
Again a commercial format written in the late eighties by Amy Hendrickson. I have a manual but not the sources. From the samples in there it is an early approach to structured documents (covering lists, tables, indexes, figures, etc). Formatting directives and style of commmand syntax is more in plainTeX style (similar to the amsTeX family of commands) but structurally going in the direction of LaTeX. I believe it became free at some point, but I couldn't find any trace on the web. Anyway, I think Amy abandoned it for LaTeX :-) given her resume.
In the early nineties Yannis Haralambous worked on a package to support writing in complex scripts. It was commercialized and perhaps for that reason not much known other than through talks given by Yannis. Eventually the numerous problems to support such scripts lead to the development of the Omega processor. You can find traces of this system still on the web, for example an article in Cahiers Gutenberg or an annoucement of its availibility and price.
A summary of its functionality is:
I'm fairly sure that it was based on top of plain TeX in those days, but not having used it myself this is just a guess.
In the olden days, AMS-TeX; it was written by Michael Spivak for the AMS and featured the alignment environments for multiple equations we are familiar with:
No *-version, as AMS-TeX didn't do any automatic numbering. It provided
There was also
to produce theorem statements; it was easily configurable for accommodating numbers. Also
It had interfaces for the AMS symbol fonts and featured also
It provided also a "preprint" style,
It had also a nice way to cope with simple bibliographies and a primitive way to build (rectangular) commutative diagrams.
The nicest feature was the manual: "The Joy of TeX", whose structure is strictly modelled on the famous "The Joy of Sex", with the same chapter titles. :)
Spivak also wrote a package on top of AMS-TeX, LAMS-TeX, that he sold. The "L" recalled "LaTeX": the format featured automatic numbering, cross-references, bibliographies with BibTeX and also an environment for pictures, particularly for commutative diagrams with diagonal arrows.
This package never really caught on, mainly because it was commercial. The macros are now in the public domain, but not the manual, and so they are unusable.
TCI Software Research's TCITeX, http://www.mackichan.com/index.html?techtalk/qtcilatex.html~mainFrame, "Added 07/24/96". Is it still in use? It is buried in the belly of SW/SWP, thus it is kind of used (although I would discourage this).