Does everybody know that you can do calculator actions directly in Spotlight in Leopard?
I use it for arithmetic, but it will do most scientific functions if you know the syntax. Trig functions are intuitive, but others (pow(x,y) for xy instead of x^y) are less so to me. As usual, intuitiveness is in inverse proportion to the need to know syntax. Search Calculator's help for 'abbreviations' to see a complete list of functions.