Monitor LAMP on Centos
While not applicable for projects I based on Amazon Cloud Infrastructure when it comes to dedicated hosting on a third party hosting providers network, two tools I find extremely useful and easy to use for my LAMP based server monitoring projects are Munin (http://munin-monitoring.org/) and Monit (http://mmonit.com/monit/)
This is a very good how-to on using both these tools
Its basic but aside from the standard monitoring plugins available for munin that monitor load averages, cpu usage, memory usage etc you can also get it to monitor items such as mysql queries, mysql slow queries, web requests etc. So its well worth checking out.
Monit is also very useful for monitoring and restarting services on your LAMP box. For example say you wanted to restart your httpd process if the load average on your server exceeded 5 for the past five minutes. Monit is an ideal tool for this.