Free Telnet/SSH Clients
TTSSH: An SSH Extension to Teraterm
TTSSH is a free SSH client for Windows. It is implemented as an extension DLL for Teraterm Pro. Source code is available.
PuTTY: A Free Telnet/SSH Client
PuTTY is a free implementation of Telnet and SSH for Win32 and Unix platforms, along with an xterm terminal emulator
OpenSSH
OpenSSH is a free version of the SSH protocol suite of network connectivity tools that increasing numbers of people on the Internet are coming to rely on.