Calculating electrical resistance is not something I have to do on a regular basis, but for those of you that do, PalmRes may be a good option.
PalmRes allows you to to calculate electrical resistance based on the four colors of an electrical resistor. Using the program is very straightforward and simply involves selecting colors from a drop-down list for the two bands, the multiplier, and the tolerance.
Once you've entered this information, the electrical resistance based on the settings you entered is displayed in ohms at the bottom of the screen.
You can also customize the degree of variance using the drop-down menu (although you can't enter you own figures here).
PalmRes is strictly an application for those who are in the know about electrical resistance, and it offers no help to those who are uninitiated.