GNU Aspell is a spell checker designed to eventually replace Ispell. It can either be used as a library or as an independent spell checker. Its main feature is that it does a superior job of suggesting possible replacements for a misspelled word than just about any other spell checker out there for the English language. Unlike Ispell, Aspell can also easily check documents in UTF-8 without having to use a special dictionary. Aspell will also do its best to respect the current locale setting. Other advantages over Ispell include support for using multiple dictionaries at once and intelligently handling personal dictionaries when more than one Aspell process is open at once.
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.
KDevelop is an integrated development environment which makes the creation and development of applications an easy task even for beginners. Highlights of the current release are: an application wizard for easy creation of KDE 4, Qt4, GNOME, and terminal C/C++ projects, full project management, a syntax-highlighting editor, code completion, an integrated dialog editor for the Qt/KDE GUI libraries, an internal debugger, a full-featured class browser with class tools, CVS and SVN support, an integrated HTML-based help system offering manuals and class-references, and extensive search mechanisms to browse sources and documentation.
Poedit is a gettext translation (.po file) editor for Unix, Windows, and OS X. It aims to provide translators with a simple, easy to use user interface with all the essential tools such as spellchecker or translation memory. It can also be used to manage translations for small projects.
Setedit is a text editor specially designed for programmers. It has a nice interface with mouse support, menus and windows (text mode). The editor is a very good choice for people with DOS background, especially people accustomed to Worstar and Borland editors. The editor has overlapped windows so you can see more than one file at the same time, configurable syntax highlighting, macros, rectangular selection, block indentation, as well as customizable keyboard shortcuts and menus.
wxDesigner is a dialog editor and RAD tool for the wxWindows C++ library and its popular Python and Perl bindings. It includes a visual dialog editor, a bitmap editor, a syntax-highlighting source editor, and built-in mechanisms for automatic generation of file skeletons, GUI classes, event handlers, and getter functions. It provides an identical user interface and identical functionality for C++, Perl, and Python, and it can generate output in C++, Python, Perl, and XML.