Cacti
Cacti is a complete frontend to RRDTool. It stores all of the necessary information to create graphs and populate them with data in a MySQL database.
Homepage: http://www.cacti.net/
Component monitoring (services and what-have-you)
- Apache
- Nginx
- MySQL - see http://forums.cacti.net/about11010.html
- BIND9 - see http://forums.cacti.net/about3018.html
- memcached
- lmSensors - see http://forums.cacti.net/about11590.html