Miramath!

Mathcad is engineering calculation software that drives innovation and offers significant process productivity advantages for product development and engineering design projects.

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.

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.

Swift Calcs enables users to effortlessly create and collaborate on interactive computational documents, from any device. Swift Calcs is bringing modern cloud­based, user­centric design paradigms to computational software.

CompPad is an OpenOffice extension to provide live mathematical and engineering calculations within a Writer document, allowing calculations to be documented using all of the resources of OpenOffice. It will have functionality similar to Mathcad, but is not intended to be a Mathcad clone. Rather, I hope it might prove more flexible and extensible, and that it might encourage other free / open-source alternatives to a proprietary engineering "Killer App."