Reusing existing OpenSSH v4 connections
I've recently learnt of an interesting new features of OpenSSH v4 which allows you to reuse open connections when connecting to the same host more than once. If you regularly have multiple open connections to a single host this is a big timesaver.
This takes advantage of a new option "ControlMaster". It means that you can setup a socket in the path ControlPath, and this socket will be used when you reconnect to the given host.