x11vnc allows one to remotely view and interact with real X displays (i.e. a display corresponding to a physical monitor, keyboard, and mouse) with any VNC viewer. It is designed to be compatible with all Unix variants and Mac OS X, and depends on a small set of standard libraries. It supports SSL/TLS and VeNCrypt encryption, Unix password logins, single port access, Zeroconf, file transfer, and UltraVNC extensions. It is part of the LibVNCServer project.
rlwrap is a readline wrapper, a small utility that uses the GNU readline library to allow the editing of keyboard input for any other command. It maintains a separate input history for each command, and can TAB-expand words using all previously seen words and/or a user-specified file.
Eterm is a vt102 terminal emulator intended as a replacement for xterm. It is designed with a Freedom of Choice philosophy, leaving as much power, flexibility, and freedom as possible in the hands of the user. It is designed to look good and work well, but takes a feature-rich approach rather than one of minimalism. Current features include color support, background images (all Imlib-supported formats), theme support, and pseudo-transparency.
Conserver provides remote access to serial port consoles and logs all data to a central host. Local and network serial connections are supported. Server console history can be replayed from the console app even if the server is down, and multiple users can connect to a single serial connection.
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.
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.