The Haloe (aka Syslog) plugin is an cacti integrated interface to a MySQL database that can be used to log events from scripts, cacti, or whatever.
It is the console component for a light weight monitoring addon for cacti. Because the database schema is based on syslog,it can be configured to use a syslog-ng or kiwi's syslogd for windows database so events can be correlated.
You will need an external program such as MSyslog, Syslog-NG, or Kiwi Syslogd to log the events to the MySQL database. This plugin is used to view and alert on events only, not the capturing of them.
A newer, PHP-based version of the script below. Makes images like the to the right. The logic being that it's easier for Cacti users if they don't need to fill a load of perl dependencies. It doesn't require Cacti, or even rrdtool, however.