Munin is a smaller and more recent tool than either Nagios or Cacti. It uses the same RRDTool data analysis structure as Cacti, with an emphasis on making it easy to create new visualization plug-ins. It can integrate into the Nagios alerting structure. The http://www.postgresql.org/ site uses it in that way, combining a Nagios based alerting system with the more powerful graphing capabilities of Munin. There is a PostgreSQL plugin for Munin that supports the basic server monitoring tasks, but not the sort of complicated derived views that check_postgres supports.
Munin is also one of the easiest monitoring projects to get started with and develop additions to. If you set up Munin to monitor hosts and just turn on all of the recommended ...
