The Calculated Column is great way to extend a list or data and to have many of the functions that Excel has.

You will find links to the right that outline the basic functions that are available to use. My Blog will show solutions that I have used.

To get started look at the links that start with MS, they will give a Microsoft document view of the formula and functions.

Calculated Column can also have HTML, look at my TopicPoint on this one to see what undocumented things you can do.