MC is a console file manager with many features such as archive handling and ftp support.
It has a very nice editor that does syntax highlighting for many languages and has many features.
It should be noted that the editor can be run independently by running *mcedit*.
MC is a vital tool for anyone who does lots of file management in the console.
htop is an ncurses replacement for top with many nice features such as process trees, scrolling the process list, and easy process management.
Nano is a light console text editor that is easy to use and supports syntax highlighting of any file type you feel like writing a syntax highlighting definition for.
From the Screen man page:
Screen is a full-screen window manager that multiplexes a physical ter- minal between several processes (typically interactive shells). Each virtual terminal provides the functions of a DEC VT100 terminal and, in addition, several control functions from the ISO 6429 (ECMA 48, ANSI X3.64) and ISO 2022 standards (e.g. insert/delete line and support for multiple character sets). There is a scrollback history buffer for each virtual terminal and a copy-and-paste mechanism that allows moving text regions between windows.To put it simply, screen is a console application that gives you multiple terminals in one and makes it easy to manage them and switch between them.
Irssi is a console IRC client that is very powerful and feature filled.
It supports useful IRC features such as multiple server support at DCC capabilities.
It is easy to use and very expandable.
For a very powerful setup, combine Screen, Irssi, and BitlBee.
BitlBee is an IRC to IM gateway that runs as an IRC server.
While it doesn't support fancy features such as file transfers and voice chat, it allows you to chat with your contacts from most IM networks from any IRC client.
You can run your own BitlBee server or connect to a public one (check the BitlBee web site).