One of my favorite SSH tricks is using the ControlMaster and ControlPath options for speeding up connections. The idea is simple: if you're already logged into a server and you need to log in again, just reuse the connection you already have instead of redoing the entire connection handshake. In addition to making connections much faster, if you're logging in with a password, you don't have to re-type your password for each connection. This can be really handy if you're doing a lot of copies with scp, checking out files with Subversion's svn+ssh://, etc., and don't want (SSH keys can also solve this problem in many cases, but requires you to set up keys on the server, whereas this just requires client-side configuration.)
Setting this up is easy. We'll designate one ssh process as a master, and then when another ssh process wants to connect to the same host, it will connect to the master process instead and request a shared connection. In order to make this work, we first have to set up a place for this master process to listen for requests.
to your ~/.ssh/config file. You can read more about the syntax in the ssh_config man page; this particular setting puts the shared sockets in your ~/.ssh directory, which is usually a good place for it, and makes sure that the path is unique for each hostname, port, and remote username, as recommended by the man page.