Collects data about network useage using libpcap.
Batch system monitoring and archiving
Active-probing-based network IDS for wireless networks
Automated Bitcoin mining monitor and up-time enforcer
NetStress is a DDoS and network stress testing tool.
School assignment for a simple network traffic analyzer
Send steganographed text messages to mtr with fake hops in the network
Bandwidth Monitoring Tool; Console SNMP traffic monitor
Monitoring your infrastructure for free.
SpiderOak Nagios check
nagios-statd patch for use with python >= 2.6
Open Source System and Network Monitoring for Linux Desktop
Organizing the Knowledge of Humanity
WatchTower is a cloud server monitoring and management tool
...a work in progress.