Complex Numbers Websites:
orefa.com
Add Up: multi-purpose calculator/converter, finance, science, statistics,...
Multi-purpose calculator/converter: finance, science, statistics, date and time, convert units: meter inch foot yard mile centimeter metre gram ounce pound kilogram kg liter...
mathnotepad.com
Math Notepad
Math Notepad is a web based editor to do mathematical calculations and plot graphs. It supports real and complex numbers, matrices, and units.