I’ve recently written two articles for SDL Tridion World, SDL Tridion’s Community Website on the subject of the Object Cache. SDL Tridion’s Object Cache is a Content Delivery side component that caches frequently used objects in memory for greater performance. Both articles provide a simple overview into the functionality of the Object Cache itself and how to use it and the other on using JMS to invalidate remote caches, a feature available since the R5.3 GA release.

You can view these articles on SDL Tridion World and they are:

What is the SDL Tridion Object Cache?

and

Using SDL Tridion Object Caching With Apache Active MQ