PuTTY is a free implementation of the Telnet and SSH protocols for Windows. Its current version supports Telnet, SSHv1, SSHv2, Secure copy, Secure FTP, and rlogin. It provides a client only version of each protocol for the Windows platform.
PuTTY boasts an impressive set of features that are often only found on commercial packages. Its SSH client is robust and feature-rich, and the Telnet support is far superior to the standard Telnet client that ships with Windows.
The official PuTTY web site is http://www.chiark.greenend.org.uk/~sgtatham/putty/. This site contains documentation and other useful information about the package. You can download the software via FTP from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html.