Ohm’s Law Calculator – This site contains a number of useful online calculators for items ranging from Ohm’s Law, Voltage Dividers, LED Biasing, and 555 Timers.
Standard Resistor Value Calculator – This calculator will select the closest standard resistor value, from 1% 5% or 10% standard EIA values, calculates the error, and prints out a table of the standard values for the given tolerance.
Resistor Color Code Calculator – This tool is designed to find the resistance and tolerance values of through hole resistors.