If there are any ssh clients I missed here that you like to use give the app a shout out in the comments.
Microsoft Windows XP, Vista, 7
Putty is the classic ssh application for windows. It is free and works well. Once you have downloaded and run the application you will get a window that lets you create a store multiple profiles. So you can put in a username, ssh server IP, password, etc. Then you can save that setup and easily connect to another device running ssh.
Microsoft Windows 8
I haven’t used Windows 8 yet and don’t currently know of any ssh clients. If you know of one drop it in the comments and I’ll add it to the post.
The built in Linux terminal is all you will need to access ssh and connect to a network device. If you are running your linux system with a graphical user interface, you will be able to find the terminal listed in utilities or applications on most linux systems. If you don’t have a graphical user interface on your system, the prompt that you have in front of you is the terminal application. To ssh using the terminal in Linux type “ssh <username>@<IP or DNS>”. It will look something like “ssh firstname.lastname@example.org”.
Apple OS X
All versions of Apple OS X have a terminal application built-in called “Terminal” that has access to an ssh command. The terminal app is located in your applications folder inside the folder “Utilities”. Once you open the terminal window you can use ssh by typing “ssh <username>@<IP or DNS>”. It will look something like “ssh email@example.com”.
My primary system has been an OS X computer for a few years now and have grown familiar with apples built in terminal application. There are other terminal applications that you can get like iTerm2 that add extra features like mouseless copy, instant replay, etc. But these feature aren’t required for basic ssh capability. The built in terminal application will work just fine for most.
Apple iOS and Google Android
There are a number of ssh clients available for Apple iOS and Google Android devices. I’ve used TouchTerm (iOS only) and ServerAuditor (iOS and Android) on my iPhone and have had good luck with these clients.