Why might you want to run an SSH client in your browser? For one thing, it is nice to install if you are already using Portable Firefox because you essentially bring an SSH client with you as well. A second reason is that many organizations restrict the ability to install software on your machine, but if you are able to install a browser plugin you can have easy access to SSH on other computers - as long as the ports are open on the firewall.
FireSSH is still in development but it is already a neat way to get access to your machines remotely and shows a lot of promise.
After installing the FireSSH addon you simply use the ssh: protocol to connect to a remote machine. For example if you want to connect to 192.168.1.1 using the user "username" you would type in or bookmark ssh://[email protected] It then prompts you for the password.
The options dialog does give some options such as timeout and proxy settings. One noticably missing feature is the ability to use an openssh key to login. Since I use this almost exclusively it won't yet be my daily SSH client but definitely is a client I'll keep in my tool chest.
FireSSH works in Firefox 4.+ only.