I was thinking about the fact that most of us are often in need of making simple (or not so simple) calculations quickly,
Here is a list of some of the calculations and conversions you can get done with Google Calculator:
http://www.googleguide.com/help/calculator.html
(among these are operations in binary and hex, log in base 2 [lg], modulo division, automatic handling of units...) I think it can make you more productive and I hope you find it useful. By the way you can also write your own script to get the power and versatility of Google Calculator to your command line. It gives you the convenience of having access to all those features simply from the terminal window.