Killing a dead ssh connection
One feature telnet has and I always missed from ssh was the ^] shortcut, giving you a way to terminate the connection.
ssh has a similar feature. If you setup 'escape characters', you can terminate the connection by typing '~.' Just add the following to your .ssh/config:
Host * EscapeChar ~
You can change the character here too, but ~ is the default and a sensible one.
If you're dealing with crappy ssh connections that often terminate, you can add the following to make the client send a keep-alive package every 60 seconds:
Host * ServerAliveInterval 60