Below are links to a number of calculators you may find useful. If it is for critical work double check the results, particularly on calculators on websites that allow anyone to submit their own calculator.
A graphing calculator from desmos.com
Click here for a simple derivative solver.
Click here for simple integration calculator.
Click here for 3 row matrix calculator
Click here for a nicer calculator solving matrix problems
Click here for calculator solving equations with variables on both sides.
Click here for calculator for polynomial long division.
Click here for complex number calculator.
Click here for quadratic equation calculator.
Click here for cubic equation calculator.
If looking for a calculator that is not here you could try one of the following:
www.wolframalpha.com/widgets Note: the Wolframalpha widgets require flash.
http://www.emathhelp.net/calculators/
http://www.mathsisfun.com/math-tools.html
Graph Paper Templates
Click here for linear graph paper template which you can print.
Click here for centimetre squared paper template which you can print.
Click here for semi-log paper template which you can print.
Galway Maths Grinds 
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