pg_activity is a top like application for PostgreSQL server activity
An eye on your system
Python library and shell utilities to monitor filesystem events
Zenoss - Intelligent IT Operations Management
Tool to ping hosts through firewalls blocking ICMP
Network Ping time and UPS Logger
Scalable, distributed monitoring system for high-performance computing
Highly configurable SNMPv1/v2c/v3 application-level proxy
Network performance monitoring and logging script for Cisco devices.
Automated Bitcoin mining monitor and up-time enforcer
Monitoring your infrastructure for free.
nagios-statd patch for use with python >= 2.6