[fatal1980]

You will want to turn persistent connections off, its really only good for small boards. You will also want to run "mysqlreport" which will give you details on what is going on with your MySQL server. It will show you details like amount of table and query cache available and used.

You should also really consider using lighttpd with php running through fastcgi. We have a site up that gets 300 requests a second and up to 3000 users online running on a Core2Duo, 4G mem, and sata drives. And it hardly ever has issues, and the load only peaks at 25 when its absolutely busy.

Setup memcache for the vb datastore and xcache for the php opcode caching. Both of these will help a ton with caching regular requests out of the box with no configuration.

Next would be caching content like images, javascript and css. This will drop the amount of connections and load by 15%. A 1 hour cache on images is good. Just remember that your users won't see any changes to images, javascript or css for an hour unless they clear their cache.