On his blog today, Justin Silverton has posted this brief new tutorial covering the use of PEAR's cache_lite package.
Cache_lite is a php/pear caching module that is designed for high traffic sites. It is different than most caching systems because it has a built-in locking mechanism that will prevent cache corruption that can sometimes occur when there are a large amount of concurrent users trying to read and write to your cached data.
He wastes no time getting to the examples, showing first a very basic example of chacing/looking for a cache of your data. There's no installation HOWTO, but if you're familiar with the PEAR system, installation should be a simple matter.