IM program supporting many protocols, including Yahoo!, AIM, IRC, or WLM; comes with the Pidgin project

The best CLI client for Slack, because everything is terrible!

Telegram client on your terminal.

Downloads videos from YouTube and some other sites; useful for automated bulk downloads.

aims to be a "easy-to-use and unbloated client for the UNIX and UNIX-like console".

Synchronizes a local copy of a website with a remote copy on a server; does not use SSH/scp but FTP for file copy; useful when the remote server does not support secure copy.

Mirror directories across networked machines; handles diffs/changed files; works across SSH; plenty of parameters.

"An open source tool that lets you securely and anonymously share a file of any size."

The program allows transfer arbitrary-sized files and directories (or short pieces of text) from one computer to another.

The two endpoints are identified by using identical human-readable codes.

"Sophisticated ftp/http client, and a file transfer program supporting a number of network protocols"; support for bookmarks and mirroring features.

A lightweight, Free Software, cross-platform BitTorrent client; a terminal curses interface, web interface and command line client can connect to a running daemon to manage torrent downloads.

A tool and library for transferring data with URL syntax; supports a lot of protocols.

Lightweight and easy-to-use download utility; it supports HTTP/HTTPS, FTP, SFTP, BitTorrent, Metalink and multiple sources; cross-platform.

Curses front-end for Remind written in OCaml with vertically scrollable time table.

A comand line interface to manage hierarchical todos. Each task has a title, a long text description, a deadline (tudu warns you when the date is close), and a scheduled date. There are categories and priorities.

A minimal clone of Wunderlist, with 30% of its features. GTD oriented. It stores the task list in a hidden JSON file in the home directory, making it easy to backup or share them.

Minimalistic todo manager that uses a simple plain text file to keep track of items; implemented as a shell script.

Todo manager with advanced features; dedicated synchronization server available; many plugins and related tools; healthy software project.

Calendar program for Unix/Linux systems that can keep track of events; custom, plain text storage format; interesting and fully functional.

Project-based todo manager: every task must be specified with a mandatory project indication. Tasks are stored within a SQLlite DB. Written in Python.