Zend certified PHP/Magento developer

How can I get all the benefits of restarting my computer without actually rebooting it?

There are a lot of different reasons why a reboot would be beneficial for the system (like flushing RAM), and all the applications that might be running for a while. However, if we wanted to get to a reboot state without actually performing a reboot, what would it take (eg: applications to kill, delete temp files, clear cache, etc)?

I’m currently on GNU/Linux but would be interested to know for any operating system.