If you're a fan of
PuTTY Portable is a Telnet Client and SSH Server for Windows that is packed with features and can be transported anywhere on a USB stick or external storage device. Whats more, it's completely free. Firstly however, note that the developer issues a warning on the program website that PuTTY Portable may not be legal in your country so check the law before you use it!
Basically, PuTTY Portable allows you to connect to another computer remotely using the Telnet and SSH protocols. So for example, you can install it on a Windows machine and it will connect to a Unix machine. This is great if you are administrator as you can use PuTTY Portable to take full control of the machine and work at it remotely.
In the PuTTY window that's opened, you can send messages to the other machine and vice versa. This leads to one of the major annoyances when using PuTTY Portable - the program does not remember the credentials for successive logins. This is understandable for security reasons, but could end up being very annoying if you use PuTTY Portable to regularly connect to an external client.
If you need to control a remote computer and need a client that supports SSH, then PuTTY Portable is a superb option considering that it's totally free and portable.