I think nowadays there's no need to use fastcgi, if you can run a native module like mod_fcgid. A few weeks ago I was playing with fastcgi but I found its configuration not so straightforward if you want to use it in many different virtual domains.
At that time I wrote this notes
http://notes.sagredo.eu/node/151 concerning the problem of running two php versions on the same apache web server with mod_fcgid