Mintty is a terminal emulator for Cygwin and MSYS with a native Windows user interface and minimalist design. It is based on parts of PuTTY by Simon Tatham and provides xterm-compatible terminal emulation, but does not require an X server. Its features include a simple options dialog, Unicode support, fullscreen mode, drag & drop, and window transparency.
(Serial Ports on) Steroids enables users to execute remote C functions in a Python shell over a serial interface. It is useful for embedded system testing and industrial automation. It generates C code for the target and a Python script for the host automatically from a C header file.
KildClient is a MUD client written with the GTK+ windowing toolkit. It supports many common features of other clients, such as triggers, gags, aliases, macros, timers, and much more. But its main feature is the built-in Perl interpreter. At any moment, the user can execute Perl statements and functions to do things much more powerful than simply sending text the the MUD. Perl statements can also be run, for example, as the action of a trigger, allowing you to do complex things.
XMins is a distribution of the XWin server, a version of Xorg's X11 server that runs on Windows. It allows you to start an X server to access an XDMCP-enabled host or to launch remote applications. Its main advantage over the XWin server distributed by Cygwin is that it doesn't require the installation of Cygwin.
Mrxvt (previously known as materm) is a multi-tab X terminal emulator based on rxvt/aterm. It supports multiple tabs, runtime dynamic tab title, pseudo-transparent backgrounds, user-supplied background images (JPEG, PNG, or XPM), background color tinting, text shadows, NeXT/rxvt/xterm/SGI style scrollbars, XIM, multiple languages (Chinese, Korean, and Japanese) and logging. It is lightweight and fast, and only depends on Xlib.
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.