Dipstick Klever Group
T42 is a free, open source implementation of unix ntalk protocol. Built in "personal secretary" will record your missing calls for you, akin to answering machine.
PumpKIN is an opensource, fully functional, free TFTP server and TFTP client, which implements TFTP according to RFC1350.
KLog is a free, open source Win32 implementation of *nix syslog daemon to support remote logging of message from syslog-enabled unix servers, routers and other networked devices and applications.
KINSole is a free, open source Win32 implementation of client side of the telnet protocol, described in detail in the RFC854 and related RFCs. It uses win32 console API and therefore may run both windowed and in fullscreen character mode.
Big Brother is the simplest tool for monitoring your IP-network for troubles. It gives you a comprehensive picture of what happened to any point on the Net that you put in.