PHP Shell is a shell wrapped in a PHP script. It's a tool you can use to execute arbiritary shell-commands or browse the filesystem on your remote Web server. This replaces, to a degree, a normal telnet-connection. You can use it for administration and maintenance of your Web site using commands like ps, free, du, df, and more.
The xterm program is the standard terminal emulator for the X Window System. It provides DEC VT102/VT220 and Tektronix 4014 compatible terminals for programs that can't use the window system directly. If the underlying operating system supports terminal resizing capabilities (for example, the SIGWINCH signal in systems derived from 4.3bsd), xterm will use the facilities to notify programs running in the window whenever it is resized.
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.
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.
MacTerm (formerly MacTelnet) is a complete terminal emulator for Mac OS X, for use with local or remote applications. It is also available for Classic Mac OS as a remote-only shell. It supports VT100, VT102, VT220, and parts of XTerm and ANSI, UTF-8 and other character sets, very accurate rendering of CP437 for use in BBS games, regular or tabbed windows, a full screen mode that works on up to two displays, dynamic search, powerful macros for entering text, running commands, and opening URLs, extensive preferences, including a flexible coloring and formatting system, Workspaces that spawn commands and auto-arrange windows, Growl notifications, text capture, floating keypads for control keys, and much more.
Cancan is a text-based, interactive utility similar to telnet, but with a number of extensions useful for MUD playing. Another use might be to provide line editing, aliases, etc., for those services that have a simple telnet interface. Cancan features aliases, actions, key bindings, text highlighting, substitutions, and line editing with history and completion.