Mac OS X Leopard only: Run quick calculations from Leopard’s Spotlight search box. Enter your formula and the answer will appear as you type, similar to how it works in Firefox’s Google search box. Google’s implementation is a tad better; it can do metric conversion (try 24km in miles), but Spotlight’s good for pure math.
Spotlight [via Hawk Wings]Windows only: Take your Windows calculations to the next level with freeware Windows app Powertoy Power Calculator. With advanced features like a built-in graphing tool, mathematical functions, tons of unit conversions, and (my favorite) a built-in history (like a running tape), this freeware, Windows only utility has surprisingly missed a featured mention on Lifehacker until now. There are tonnes of free calculators available for Windows, but the Windows Powertoy Calculator is a perennial favorite. While you’re at it, check out these other power replacements for built-in Windows utilities.
Microsoft Powertoys for Windows XP [Microsoft]
