HE.NET Network Tools - This suite of networks tools implements most of the network diagnostics that you need as a Network...

ipcalc - IP Calculator. ipcalc takes an IP address and netmask and calculates the resulting broadcast, network, Cisco wildcard mask, and host range. By giving a second netmask, you can design subnets and supernets....

OONI Probe - Mobile app from Tor Project to check if you're censored.

Radmin - With Radmin, provide instant remote tech support to corporate network users. Gain secure remote access to network computers and servers.

PowerPing - Advanced command-line ping tool, lovingly inspired by Windows and Linux native tools.

whatmask - Whatmask is a small C program that will help you with network settings and subnet calculations.