The standard joomla Cache plugin works great, but if your template creates a mobile view for mobile users your worst dream may come true!
If an iphone user visits the page, joomla will create the cache and will serve it to all users. This would be fine for your iphone users, but desktop users visiting the page will wonder why the page has just one column???

This small plugin extends the joomla cache plugin and creates separate cache file for mobile devices. This way users coming with an iphone(or other mobile device) will see the cached mobile version and users visiting the page with a desktop browser will see the normal version of the page.