One of the best options for SSH on Windows is SecureCRT, from http://www.vandyke.com/. It is a commercial product but we have a large number of licenses for an old-ish but useful version (5.0.5). You can download the installer from MyPhys, along with the license information. We have some basic directions for using SecureCRT.
Also available from MyPhys is an even older but still-functional SSH Secure Shell Client (from ssh.com). The installation includes a Secure File Transfer client which is a very useful replacement for FTP.
You can obtain installers for the above programs from our MyPhys software download page.
There are also a few free clients, such as PuTTY.
An excellent program available for free evaluation is MobaXterm, which includes a tabbed ssh client, secure file transfer, an X11 server, and many other features. Only the “home edition” is free, so please make sure you abide by their license terms.
For file transfer (SCP or SFTP), we suggest using SSH Secure Shell Client (above), or WinSCP.
If you want, you may also purchase Expandrive, which can map a remote filesystem over ssh as a windows drive.
SSH is provided with Mac OS already, for command line use.
Unix and Mac OS X users can use OpenSSH to provide SSH and SFTP servers
A few SSH servers are available for Windows systems. Although they should not be installed carelessly, they may be useful for secure file transfer or other purposes.