[markh]

fastcgi with Apache will be a waste of your time I think.

Apache+php is solid, but a memory hog. If you want to keep things simple, move to Nginx with php+fastcgi. This is the suggested config for Slicehost.

Or, as previously suggested, offload the client connection to an Nginx server sitting in front of Apache. This will relieve the pressure on the php instances and will also handle static file serving.