Since years I used the ‘bc’ unix command line calculator. Nice for copy paste jobs, better than a push button calculator, since you can see your calculators. Of course pretty stupid otherwise. I am sure there are advanced calculators around. Those that I would always forget how to use. Speaking of, ‘bc’ needs you to set the decimal precision before something like 5 / 3 gives a result as usually expected. Every couple of month I am trying to find a way to set scale = 4 in a default environment etc. Never had any luck.
Today osxhints – which comes up first for most unix searches these days – I found the Google Command Line Calculator
It’s very very nice. Written in ruby which comes with OS X. Commandline, but that’s what I liked.