Further, I discovered how you can use your own identity even after logging into your server. For example, if you use ssh for git, and wanted to be yourself when doing, say, a git push from a remote server, you can use the following in your configuration file:

ForwardAgent yes

A note of caution. On the Mac, a reboot causes the ssh-agent to forget the keys available for forwarding, so after every reboot, you will also have to execute:

$ ssh-add ~/.ssh/id_rsa

To check whether your key is already present in the key list, you could do:

$ ssh-add -L

Please post this kind of newbie/101 stuff elsewhere...

I also have a lot of ssh-shortprojectordomainname aliases. These different logins, IPs and ports are complicated to remember and to write every time. Usually I am also logging into a specific directory.