GNS3 - Cisco Graphical Network Simulator

Introduction
Another great product from open source community. If you have read Dynagen and Dynamips then this will enhance your experience in cisco simulation. GNS3 offers complex graphical network simulator and launch simulation on them.
Features currently supported by GNS 3 are:

Designing high quality complex network topologies.
Emulating Cisco routers and PIX firewalls.
Simulating simple Ethernet, ATM and Frame [...]

JFFNMS Open Source Network Monitoring System

Description
JFFNMS stands for Just For Fun Network Monitoring System. Yes it will make network administrator has fun time with their network :). JFFNMS is developed by Javier Szyszlican. What it makes a special NMS software is a lot of feature for fault management and performance management.
Here is the feature i can highlight from JFFNMS website:

Multi [...]