Advanced Subnet Calculator (Network Internet -/- Other) [Release Date 08.10.2007]
Free Subnet Calculator tool from SolarWinds generates all subnets with real-time DNS, PING and CIDR tests. This application provides address details, a classful subnet creator, a CIDR calculator and subnet address lists that can be exported.

SemSim CCNA Subnetting Tutorial (Network Internet -/- Other) [Release Date 23.09.2004]
SemSim CCNA subnetting tutorial & practice questions. Subnetting is explained with examples. Learn to subnet and understand concepts such as subnet mask and ip addressing. The tutorial is follwed by a subnetting quiz to test your understanding.

Subnetting Calculator (Business -/- Calculators Converters) [Release Date 16.05.2004]
Subnetting Calculator.NET was designed with network administrators in mind. Just enter in the the IP address or Network address and the select the Subnetmask. You will then know what network the address is on, all other networks available