qcon turns any terminal emulator for X into a Quake-style console. It is similar to tilda, kuake, and similar programs, but is't a terminal emulator by itself. Instead, qcon uses your favorite one, controlling its window position and state. It should work with most popular window managers and desktop enviroments.
Qodem is a re-implementation of the Qmodem DOS shareware communications package, updated for more modern uses. Major features include Unicode support, scrollback buffer, capture file, screen dump, dialing directory, keyboard macros, script support, Xmodem, Ymodem, Zmodem, and Kermit. It can connect over serial port, telnet, ssh, rlogin, and command line, and supports multiple terminal emulations including ANSI.SYS, Avatar, VT100/102, VT220, and Linux.
rdesktop Console is a Perl/Tk based utility for Linux to work with multiple rdesktop servers. It works with rdesktop 1.1.0 from www.rdesktop.org to manage multiple sessions for logging into Windows NT and 2K Terminal Servers. It allows creation and management of a simple list of servers and a default resolution for the terminal windows.
rxvt-unicode is a clone of the well known terminal emulator rxvt, modified to store text in Unicode and to use locale-correct input and output. It also supports mixing multiple fonts at the same time, including Xft fonts, real transparency, and an optional embedded Perl interpreter that allows you to extend your terminal easily.
Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells. Each virtual terminal provides the functions of the DEC VT100 terminal and, in addition, several control functions from the ANSI X3.64 (ISO 6429) and ISO 2022 standards (e.g., insert/delete line and support for multiple character sets).