Ping Meter Gadget - Customizable, graphical, semi-transparent ping (latency) meter.
PingPlotter - PingPlotter is a troubleshooting tool that helps IT professionals and neophytes identify, diagnose, and resolve network issues.
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.
SmokePing - Smokeping is a tool for measuring latency.
NetTK - NetTK, Network Tool Kit, is an Open Source alternative for monitoring and troubleshooting your...
WinMTR - Free Network Diagnostic Tool. WinMTR is an equivalent of mtr for Windows.