Download ruby enterprise and follow instructions on page. The exact commands I used are:

$ cd ~/bin
$ wget http://rubyforge.org/frs/download.php/68719/ruby-enterprise-1.8.7-2010.01.tar.gz
$ tar xzvf ruby-enterprise-1.8.7-2010.01.tar.gz
$ cd ruby-enterprise-1.8.7-2010.01
$ rm -rf ../ruby-enterprise-1.8.7-2010.01.tar.gz
$ ./installer

I installed to /Users/me/bin/ruby-ee-1.8.7

$ cd /Users/me/bin/ruby-ee-1.8.7
$ rm -rf ~/bin/ruby-enterprise-1.8.7-2010.01/

Add this to your ~/.bashrc

#Ruby Enterprise 1.8.7
export PATH=~/bin/ruby-ee-1.8.7/bin:$PATH

On with the install (of Passenger)

~/bin/ruby-ee-1.8.7/bin/passenger-install-nginx-module

I chose option 1, to get nginx installed for me, I chose /Users/me/bin/nginx for the location.

Start the service

$ sudo ~/bin/nginx/sbin/nginx

For help and reloading

$ sudo ~/bin/nginx/sbin/nginx -h
$ sudo ~/bin/nginx/sbin/nginx -s reload

Visit 127.0.0.1 in you rbrowser and the default screen should be there. The web application that it is loading is set in:

~/bin/nginx/conf/nginx.conf

I added in a root to my Sinatra application that I have been working on:

server {
    listen       80;
    server_name  localhost;
    root /Users/morgy/Documents/Code/Amaras-Site/public;   # <--- be sure to point to 'public'!
    passenger_enabled on;
}

This then returned a 403 error… Still a little work todo will post update on resolving this.

[Update] I forgot that root had to point to the public folder inside the rack (Sinatra) application. I know there is a big comment there saying make sure but I just read that to be a permissions issue rather than the more literal a folder called public.