TEA is a powerful and easy-to-use Qt4-based editor with many useful features for HTML, Docbook, and LaTeX editing. It features a small footprint, a tabbed layout engine, support for multiple encodings, code snippets, templates, customizable hotkeys, an "open at cursor" function for HTML files and images, miscellaneous HTML tools, preview in external browser, string manipulation functions, Morse-code tools, bookmarks, syntax highlighting, and more.
LavaPE is a programming environment for the experimental object-oriented programming language Lava. It replaces text editing with structure editing, thereby preventing all syntactic and many semantic errors. The pure point-and-click nature of Lava programming and the concise representation of programs as declaration trees with small chunks of executable code simplify programming, and ease comprehension.
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.
gjots lets you organize text notes in a convenient, hierarchical way. It can be used for notes, jottings, bits and pieces, recipes, and even PINs and passwords, using encryption. It can also be used to "mind-map" larger compositions like manuals, Web pages, articles, etc. It is a bit like the KDE program "kjots", but uses the GTK library and supports a hierarchy of folders. Files can be output to HTML with an automatic table of contents or to docbook XML. Encryption is supported with ccrypt(1), gpg(1), and openssl(1), so that musings can be kept private.
FXiTe is an advanced cross-platform text editor built with the Fox GUI toolkit and the FXScintilla text widget. It features built-in syntax highlighting for 40+ languages, an embedded Lua scripting engine, macro recording and playback, multi-line regular expression search and replace, rudimentary ctags and calltip support, a flexible interface to external tools, and a built-in "message window" to capture the output of external commands such as compiler error messages, etc.
XEmacs (formerly known as Lucid Emacs) is a powerful, extensible text editor with full GUI support, initially based on an early version of GNU Emacs 19 from the Free Software Foundation and since kept up to ate with recent versions of that product. XEmacs stems from a collaboration of Lucid, Inc. with Sun Microsystems, Inc. and the University of Illinois with additional support having been provided by Amdahl Corporation, INS Engineering Corporation, and a huge amount of volunteer effort.