If your site has gotten so mired down in dynamic content that it doesn't seem like there's hope in sight, you might want to check out this new piece from DevShed.

In their latest, Caching With PHP Cache_Lite, they introduce you to this piece of the PEAR system that will allow you to cache pages and source to make your pages fly. They use a little of PHP's natural output buffering to get the job done, but the main work is in the Cache_Lite system. They even show you how to use this caching system and the SOAP interface to Amazon.com's web service to cache some results locally to speed up your user's queries.

From what I can tell, this looks like a pretty good alternative to some of the other chaning systems that are out on the market today. I've messed with the PHP Accelerator before, but I don't think that's techincally a caching system. I'd love to see some benchmarks on this stuff.