SoftSchools.com provides free math worksheets, free math games, grammar quizzes and free phonics worksheets and games. Worksheets and games are organized by grades and topics. These printable math and phonics worksheets are auto generated. You will also find tests and quizess for all subjects from social studies, to Chemistry, to Language Arts. It's a really useful website from Pre-K to high School!

http://www.softschools.com
 
You can also find online calcolaters for almost everything you can think of:
Online graphing calculator
Scientific Calculator
Factorial Calculator
Fibonacci Calculator
Probability Calculator
Trigonometry Calculator
Vector Calculator
Square Root Calculator
Cube Root Calculator
Arithmetic Progression Calculator
Cubic Equation Calculator
Quadratic Equation Calculator
Standard Deviation Calculator
Sum of Consecutive Squares Calculator
Sum of Consecutive Cubes Calculator
Annuity Calculator
Windchill Calculator
Time Speed Distance Calculator
Temperature Conversion Calculator
Sine Calculator
Relative Humidity Calculator
Percent Change Calculator
Cubic Equation Calculator
Cosine Calculator
GPS Longitude Latitude Converter
Sphere Calculator
Pythagorean Theorem Calculator
Pyramid Calculator
Math