I've been managing sites on a Linode via SFTP in the past and tonight finally got around to using SSH Key Pair Authentication instead of username/password. I have SSH Key Pair Authentication set up and working right, but now I'm wondering how can I manage files via SFTP client if username/passwords are turned off?

SFTP-capable clients usually support keypair authentication. FileZilla for example, not only supports SFTP and keypair authentication, but it can also recognize public keys currently loaded in PuTTY's Pageant authentication agent.