Total Network Inventory: Professional PC audit and network inventory management software - fits best for a for companies of all sizes. Free for 60 days.
NetSpeedMonitor - NetSpeedMonitor is a lightweight Network Monitoring Toolbar for your Windows Taskbar
Network Inventory Advisor - Network Inventory Advisor audits all network software and hardware simply and efficiently
TrafficMonitor - TrafficMonitor is a network monitoring suspension window software in Windows.
Lansweeper - Lansweeper discovers Windows, Linux and Mac machines in your network.
DU Meter - DU Meter is a network bandwidth monitor for your computer.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.