iperf - A TCP, UDP, and SCTP network bandwidth measurement tool
PingPlotter - PingPlotter is a troubleshooting tool that helps IT professionals and neophytes identify, diagnose, and resolve network issues.
SmokePing - Smokeping is a tool for measuring latency.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Multiping - Get MultiPing Support. Network monitoring in 60 seconds. MultiPing provides a graphical view of network performance, monitors hundreds of targets, and sends automatic alerts..
GPING - GPING (Graphical Ping) is a powerful utility that pings and graphs multiple hosts simultaneously...