http://quickleft.com/blog/reverse-proxying-local-servers-through-nginx

sample_nginx_config.conf

worker_processes 1;
events {
	worker_connections  1024;
}
http {
	include       mime.types;
	default_type  application/octet-stream;
	sendfile        on;
	#keepalive_timeout  0;
	keepalive_timeout  65;

	upstream upstream_server {
		server localhost:3000;
	}

	server {
		listen       80;
		server_name  my_site.local;

		location / {
			proxy_set_header X-Real-IP $remote_addr;
			proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
			proxy_set_header Host $http_host;
			proxy_redirect off;
			proxy_pass http://upstream_server;
			break;
		}
	}
}