Ping Meter Gadget - Customizable, graphical, semi-transparent ping (latency) meter.
TCPView - TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on...
PingDoctor - PingDoctor is software that is considered to be the most powerful and easiest to use network route analyzer.
CurrPorts - CurrPorts displays the list of all currently opened TCP/IP and UDP ports on your local computer.
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.
Total Network Monitor - Total Network Monitor is a network monitoring software that is designed to continuously monitor your local network, individual computers, and services. Free for 60 days.