PuTTY is a free implementation of SSH and Telnet for Windows and Unix platforms, along with an xterm terminal emulator.
A telnetd server with a IPv6 support, chroot support, allow/deny via user, IP and MAC address, and which has it's own native authentication so that telnet accounts cannot be used to log into the main system.
ExtraPuTTY is a fork of Putty 0.63 for Windows. It adds a Win32 API, command shortcuts, uses config files instead of the registry, automatic reconnection, and supports FTP, TFTP, X/Y/Zmodem besides SSH and Telnet. It also provides Lua 5.2 scripting for session handling and management, and is directory relocatable for portable installations.