Mathcad!

SMath Studio - is a math program with 'paper'-like interface and numerous computing features. It has an ability to work with systems, matrices, vectors, complex numbers, infinities and fractions. SMath Studio supports 18-th interface languages, has versions for Windows, Windows Mobile (PPC, communicators and Smartphones) and Linux. It also includes integrated mathematical reference book.

Mathematica is a computational software program used widely in scientific, engineering, and mathematical fields and other areas of technical computing.

SciPy (pronounced "Sigh Pie") is open-source software for mathematics, science, and engineering. It is also the name of a very popular conference on scientific programming with Python. The SciPy library depends on NumPy, which provides convenient and fast N-dimensional array manipulation.

Online math solver, equation library, graphing calculator and science/engineering problem helper.Calculate multiple equations at once, Edit existing formulas and Create new ones, Compute large numbers of values, Plot graphs, Link your results, Solve full problems and Share worksheets with your friends.

wxMaxima is a document based interface for the computer algebra system Maxima. wxMaxima uses wxWidgets and runs natively on Windows, X11 and Mac OS X. wxMaxima provides menus and dialogs for many common maxima commands, autocompletion, inline plots and simple animations. wxMaxima is distributed under the GPL license.

Maple is a general-purpose commercial computer algebra system. Users can enter mathematics in traditional mathematical notation. Custom user interfaces can also be created. There is support for numeric computations, to arbitrary precision, as well as symbolic computation and visualization. Examples of symbolic computations are given below.Maple incorporates a dynamically typed imperative-style programming language which resembles Pascal. The language permits variables of lexical scope. There are also interfaces to other languages (C, C#, Fortran, Java, MATLAB, and Visual Basic). There is also an interface with Excel.Maple supports MathML 2.0, a W3C format for representing and interpreting mathematical expressions, including their display in Web pages. »

Miramath is an open source project inspired by the MathCad mathematical application. The main user interface consists of a page into which mathematical expressions can be entered or edited and then evaluated.

Graphical frontend for GNU Octave. Edit formulas in native mathematical notation. Available / tested for Linux x586 / x86_64, WinXP, Vista, and MacOS.

Xcos is a graphical editor to design hybrid dynamical systems models. Models can be designed, loaded, saved, compiled and simulated.

MathStudio, formerly SpaceTime, is the most comprehensive math app available for mobile devices. Whether you need a simple calculator to do your finances or a replacement for your TI graphing calculator, MathStudio is the most powerful and versatile calculator available on the App Store and Android Market.

ASCEND is a free open-source software program for solving small to very large mathematical models. ASCEND can solve systems of non-linear equations, linear and nonlinear optimisation problems, and dynamic systems expressed in the form of differential/algebraic equations.