ssh-from simplifies common usage of SSH tunnels, and makes double (or triple) tunnels a piece of cake.
Here is an example, where I SSH to a computer that is behind two NATs, tunneling through each router:
Details coming to the blog soon.
Install dependencies (tsocks is optional):
sudo apt-get install python lsof tsocks
Then download the script somewhere in your PATH and make it executable:
sudo wget https://gist.github.com/jmendeth/346f2233310d8292efe7595d60aa3659/raw/ssh-from.py -O /usr/local/bin/ssh-from sudo chmod a+rx /usr/local/bin/ssh-from
I highly recommend you install this helper program as well.