GNU TeXmacs, is a free WYSIWYG scientific text editor based on TeX.
"The software includes a text editor with support for mathematical formulas, a small technical picture editor and a tool for making presentations from a laptop. Moreover, TeXmacs can be used as an interface for many external systems for computer algebra, numerical analysis, statistics, etc. New presentation styles can be written by the user and new features can be added to the editor using the Scheme extension language. A native spreadsheet and tools for collaborative authoring are planned for later."
"TeXmacs runs on all major Unix platforms and Windows. Documents can be saved in TeXmacs, Xml or Scheme format and printed as Postscript or PDF files. Converters exist for TeX/LaTeX and HTML/MathML."
LyX offers a full WYSIWYG front-end to LaTeX .
"LyX is a document processor that encourages an approach to writing
based on the structure of your documents, not their appearance. It is
released under a Free Software / Open Source license.
LyX is for people that write and want their writing to look great, right out
of the box. No more endless tinkering with formatting details,
'finger painting' font attributes or futzing around with page boundaries.
You just write. In the background, Prof. Knuth's legendary TeX typesetting
engine makes you look good.
On screen, LyX looks like any word processor; its printed output — or
richly cross-referenced PDF, just as readily produced — looks like
nothing else. Gone are the days of industrially bland .docs, all
looking similarly not-quite-right, yet coming out unpredictably different
on different printer drivers. Gone are the crashes 'eating' your
dissertation the evening before going to press.
LyX is stable and fully featured. It is a multi-platform, fully
internationalized application running natively on Unix/Linux and the
Macintosh and modern Windows platforms.
"
There exists a version of LyX which runs within the KDE environment, KLyX, though development of this seems to have stalled.