glogwatch is a GKrellM plugin that alllows the monitoring of an arbitrary file, such as /var/log/messages, or a SNORT alert file, for changes. Once a change is detected, a timer is displayed showing the elapsed time since the change occurred. The timer is reset and re-armed when the user clicks on the plugin to view the file.
IP Traffic Volume uses Linux kernel iptables to log incoming and outgoing bytes though your network device(s) and can dump summarized log statistics in ASCII to the console or display in HTML via the included CGI interface for displaying on a Web server. It is highly configurable as to what kind of traffic is counted, e.g. to and from specific ports and/or specific IP addresses or groups of ports and addresses. It uses a mininum of resources and doesn't need a database for the logged data.