I have faced this issue for quite some time now. I always install a new version of Ubuntu and the "Open in Terminal" option from right click menu is gone. I am not sure what changes but it used to be default in 10.10 (Maverick) as far as I remember and I hate to just open the terminal and navigate to the desired directory using cd command.
Anyway no matter what user interface you use (Like gnome or unity which is default now a days) it uses nautilus as it's default file manager and nautilus has this plugin in it. So let's see how can we install this plugin. BTW the plugin is called nautilus-open-terminal.
Installing "nautilus-open-terminal" plugin
You can very well install it from the Synaptic Package manager or Ubuntu software center but the quickest way would be command line. Execute the following command -
sudo apt-get install nautilus-open-terminal
after installation is complete you will have to restart nautilus. For that you can execute
Next time you open your file manager you can use this feature.