NetSpeedMonitor - NetSpeedMonitor is a lightweight Network Monitoring Toolbar for your Windows Taskbar
Ping Meter Gadget - Customizable, graphical, semi-transparent ping (latency) meter.
FreeMeter - Monitor network bandwidth (C#.NET 2k/XP+). Desktop and Systray graph.
Fping (open source) - fping is a program to send ICMP echo probes to network hosts, similar to ping, but much better performing when pinging multiple hosts.
NetTraffic - Essential network bandwidth monitor.
Open Nettest - Open Nettest is a platform for collecting, processing and visualizing data related QoS and QoE.