PuTTY is an SSH and telnet client, developed originally by Simon Tatham for the Windows platform. PuTTY is open source software that is available with source code and is developed and supported by a group of volunteers.
http://www.putty.org/
I have listed PuTTY first because it is very small and unobtrusive. You download it and run it, no real installation involved. You can just stick it on the desktop and if you decide to get rid of it, just toss it in the recycle bin/trash can.
TeraTerm Project would have been developed terminal emulator “Tera Term” and SSH module “TTSSH”. This software is open source software under BSD License. This is Tera Term Pro 2.3 succession version and is being officially recognized by the original author. Development is continuing in Project Page on OSDN.
https://ttssh2.osdn.jp/index.html.en
AbsoluteTelnet / SSH is a telnet and SSH client for Windows.
http://www.celestialsoftware.net/
The little blurbs about each of the above telnet clients was stolen from their individual websites.
Last Update: 05-Apr-17