NetPlug is an extensible multi-connections, multi-protocol, network client program, written in pure Tcl/Tk. Includes a complete Irc client plug in that you should love if you like IrcII 'classic' look & feel (plus customizable style/colors scheme, sound,... Now includes full DCC support (with GUI), ircII like aliases and improved scripting (Tcl!), keywords (your nick...) highlighting, and more
The Mail Users' Shell (mush) is a powerful mail program. It does have a curses (and suntools) interface but is best when used with the commandline interface. Considering that it is commandline-based, it is suprisingly simple to use and also has the advantage of being very fast and powerful. For example, you can write scripts to manipulate mail using csh-style syntax.
Dip handles the connections needed for dialup IP links, like SLIP or PPP. It can handle both incoming and outgoing connections, using password security for incoming connections. It has a command mode (an interactive program to set up an outgoing IP connection), dialout mode (interprets chat script to dial out and open an IP connection), and dialin mode (login shell for handling incoming IP connections, as in dialup SLIP and PPP connections).
Linux/IR is a project with the goal of implementing the IrDA protocol stack into the Linux kernel. IrDA is a standard for infrared communication between devices such as laptops, printers, PDAs, mobile phones, and LAN access points. LAN and printer support has been implemented, and the current release is quite stable. There are still a few problems. The IrDA layers that have been implemented are IrPHY, physical layer, stuffing and wrapping of frames, IrLAP, link layer, sliding windows and link access control, IrLMP, link management, multiplexing, IrIAS, information base, device discovery information, IrLPT, printer support, IrTTP, transport layer, flow control, IrLAN, LAN access, IrOBEX, and object exchange, so you can talk to your Palm III.
GNUnet is a peer-to-peer framework with focus on providing security. All peer-to-peer messages in the network are confidential and authenticated. The framework provides a transport abstraction layer and can currently encapsulate the network traffic in UDP, TCP, HTTP, HTTPS, or direct 802.11 (WLAN). GNUnet supports accounting to provide contributing nodes with better service. The services built on top of the framework include anonymous file sharing and a virtual network providing IPv4-IPv6 transition via protocol translation over the P2P network.
isdn4net is a collection of scripts and configuration files to help you run isdn4linux. It is designed for fast setup of a simple dialout to one ISP, but may also be used for management of complex setups. It is intended for Mandrake systems, but if there is interest, it could be adapted to others as well.