Ping Meter Gadget - Customizable, graphical, semi-transparent ping (latency) meter.
socat - socat is a relay for bidirectional data transfer between two independent data channels.
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.
Komodia Relay - Free open source tool to perform TCP based session relay
PingDoctor - PingDoctor is software that is considered to be the most powerful and easiest to use network route analyzer.
PortMapper - Do you need to map a specific TCP or UDP port on your machine to another port on another machine?