SSH into a machine with a dynamic IP
If you're using my previous method for logging a networks ever-changing public IP to a webserver you control, you can use this simple command to grab the last known IP and SSH into the box that way.
ssh USERNAME@`curl -s http://www.example.com/pong.php`
backticks, when run in a shell, will execute that command and return the results. In this case, it grabs the pong script, reading the IP address it provides, and the SSH's into it.