Benchmark on a 256mb xen vps:
apache2+mod_php+xcache = 42 req/sec
nginx+xcache+php-fpm = 150 req/sec
NginX and PHP will be compiled from Source as these are softwares with a very fast development, and pre-compiled packages are often prehistoric and are not suitable to apply custom patches (like php-Fpm).
Another article with fastcgi load balancing
To configure Nginx to load balance multiple FastCgi servers use this type of configuration
And the last line said something about php-fpm - it's first time i heard about it
If you’re using spawn-fcgi from lighttpd consider replacing it with php-fpm.
[ED: i will do it soon and got a new acronym derived from the LEMP stack
FLEPS stack (Firebird ,Linux, EngineX,PHP,SSH/SSL)]