First thing first:
- Make sure you have installed OpenSSH on the destination machine.
- ssh -R 1234:localhost:22 home_machine (where home_machine is the IP Address of your home computer)
- Once you have established the connection, from your home type: ssh your_name@localhost -p 1234
Similar Article from HowToForge: http://www.howtoforge.com/reverse-ssh-tunneling