FreeMeter - Monitor network bandwidth (C#.NET 2k/XP+). Desktop and Systray graph.
NetSpeedMonitor - NetSpeedMonitor is a lightweight Network Monitoring Toolbar for your Windows Taskbar
NetTraffic - Essential network bandwidth monitor.
trafficWatcher - trafficWatcher is a small tool to monitor your network activity.
NetBalancer - NetBalancer is a Windows application for local network traffic control and monitoring.
NetWorx - NetWorx is a simple and powerful tool that helps you objectively evaluate your bandwidth situation.