Lehi Sanchez has put together a tutorial showing how to get the combination of a Ubuntu, NGINX, Ruby, and PHP up and working.

I'm going to walk you through the process with the settings that I chose for my server setup. I am not a Linux guru or a web server guru. [...] This post is compiled of steps and configurations that I've found on the internet. I wanted to have a consolidated instruction manual so I'm writing this tutorial to help anyone who's in the same boat as me.

It's a full installation tutorial too - every step from the installation of the operating system down to installing the packages for the web server and two languages (apt-get, of course). There's even parts of the configuration files that you'll need to add/update to get it all integrated.