Something you might want to consider turning on query caching in MySQL. I’m not sure if this is what you are getting at, but MySQL has can be configured to cache query results in memory. That way, if you use the same query over and over again, it can feed the answer to it’s clients without accessing disk.
I know that the Zend Accelerator works well, but it’s expensive. Turke MMCache is the best freeware PHP accelerator for PHP4, but has some problems with PHP5. Any thoughts?
Best Freeware Available, I think, is E Accelerator (this site uses this with PHP5):
Best Payware, Zend: