If you're a Joomla! user for your site and you're trying to squeeze every last bit of performance out of it, you might want to check out this method the SOS Brigade has come up with to force modules to cache.

Sometimes only enabling Joomla! Cache from administration panel isn't enough and you need to boost your site even more. Below I will explain a trick to make all modules get cached, even if they don't get by default. It adds an option to module's parameters in the Joomla admin. You just need to add a few lines to the module's xml file in the joomla_main_folder/modules/module_folder/module_name.xml file.

By adding in a bit of additional XML, you're adding a new option to the Joomla! admin to let you turn on or off caching on a specific module (as tested on 1.5).