An eye on your system
Zenoss - Intelligent IT Operations Management
Show devices in a lan
track log files, block intrusions, and much more
Open Source SIEM
Scalable, distributed monitoring system for high-performance computing
Highly configurable SNMPv1/v2c/v3 application-level proxy
Monitoring of websites with spider and email notifications
Library for reading nfdump files
Batch system monitoring and archiving
Monitoring your infrastructure for free.
SpiderOak Nagios check
Open Source System and Network Monitoring for Linux Desktop