NumWorks - The graphing calculator that makes learning math easier.
PCalc - PCalc is the powerful choice for scientists, engineers, students, programmers, or indeed anybody...
Rule of 3 Calculator - Apply the mathematical Rule of Three in an easier, faster and more practical way!
eMathHelp.net - Site is created to help people learn math. Includes algebra, calculus, differential equation calculators and notes with many examples.
RealCalc Scientific Calculator - RealCalc Scientific Calculator
Calculator OSX App - Real Time.