Suhosin is a great and simple way of increasing your security without having a large impact on overall performance. In this tutorial I will cover the installation and configuration of Suhosin on both debian etch and centos 5. I may cover mod_security in a later tutorial.
They apt-get the packages needed for the patch in examples for two different distributions - Debian (etch) and CentOS. They also show how to set up some basic configuration to get the patch installed and working with your PHP installation.