GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
LyX is a document processor that encourages an approach to writing based on the structure of your documents, not their appearance. It is intended for people people who write and want their writing to look great without tinkering with formatting details, font attributes, or page boundaries. On screen, it looks like any word processor, but it uses the TeX engine for printed output and producing richly cross-referenced PDFs. It is stable and fully featured.
METAGRAF is a graphical editor for creating figures in MetaPost. It is currently able to draw any kind of figure in b/w or color. METAGRAF outputs a MetaPost file which can then be run through MetaPost by itself or using TeX. The program is written in Java and is thus platform-independent.
Sixpack is a graphical and command-line bibliography database manager written in Perl/Tk. It interacts with the supplied package 'bp', which can import and export from a number of formats including bibtex, endnote, medline, procite, and many others. It can download references directly off the Web, and open articles using external viewers. It can also interface with Emacs/XEmacs and Lyx.
rtf2latex2e is an utility to convert RTF files from popular word processors to the LaTeX2e format for those who value quality typesetting. rtf2latex2e uses the RTF reader package by Paul DuBois to parse the RTF code and generates an appropriate LaTeX file. The main features of rtf2latex2e are: detects text style: bold, italic, color, big, small,... reads embedded figures: PICT, WMF, PNG, JPEG,... reads tables: simple to semi- complex equations: reads out Equation Editor equations (courtesy Steve Swanson, http://www.mackichan.com) symbols: converts most greek and math symbols reads footnotes (not in tables yet), and converts hypertext links using the hyperref package.