CCCalc!

SpeedCrunch is a free, fast, high precision open source algebraic calculator with an intuitive interface and a extensive list of features, including: Unlimited Variables, Syntax Highlighting, Functions, with 'Automagic' Completion, 50 Decimal Precision, Input History and more...

Qalculate! is a multi-purpose desktop calculator for GNU/Linux and Windows. It is small and simple to use but with much power and versatility underneath. Features include customizable functions, units, arbitrary precision, plotting, and a user-friendly interface (KDE or GTK+).

Maths on a Mac as it should be. Soulver is a new kind of calculator application which uses a simple yet powerful word-processor style interface instead of the traditional "button" approach to doing math.

Windows Calculator, commonly known as Calculator from the application's title bar, is a calculation application included in all versions of the Microsoft Windows operating system. It can be activated by the command "calc" on most Windows systems.

OpalCalc is a brand new type of calculator for the PC. As easy to use as Notepad or a word processor, OpalCalc allows natural language in the sum and multi-line support so you can go back and adjust your previous calculations on the fly.

galculator is a GTK 2 / GTK 3 based calculator with ordinary notation/reverse Polish notation (RPN), a formula entry mode, different number bases (DEC, HEX, OCT, BIN) and different units of angular measure (DEG, RAD, GRAD). It supports quad-precision floating point and 112-bit binary arithmetic.

Calculator Plus is a nice addition to hundreds of Calculator apps but with unique idea and innovative and user friendly designed buttons.

A calculator written in C#.NET 3.5 that aims to be simple and usable. Future plans include functionality above and beyond that of the standard windows calculator. (Requires the .NET 3.5 framework)

Omni Calculator is a startup aiming in solving all (hence "omni" in the name) small math problems you have in your everyday life. All of their calculators offer unparalleled ease of use and functionality. They work in real time and can solve for any variable. You are able to share the result with your friends and co-workers. They can be used on web, mobile or embedded on external websites with a slick, fully functional calculator widget.

Calculator with log and printing capabilities.

Numeric Notes – is not just a totally new way to count, but also possibility to keep and share calculations on your Mac.

An online calculator that allows the free form mixing of numbers and words, and saves calculations automatically.

Features a calculator:Standard arithmetic.The calculation of trigonometric functions in degrees radian.Calculation of the exponential function, the natural logarithm, logarithm.The calculation of power functions (x to the power y, x squared, the square root of x).The calculation of interest.Memory functions.

GlassCalc is a free, Windows calculator designed for quick input via keyboard. It forgoes the usual array of buttons for a single textbox where you can type an equation or mathematical expression, hit Enter, and get a result.