SpeQ Mathematics - SpeQ is a small, extensive mathematics program with a simple, intuitive interface.
Kalk Calculator - Powerful calculator application for Linux mobile and desktop devices
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.
NumWorks - The graphing calculator that makes learning math easier.
Calculairum - Descriptive, Editable, Gesture-Based & Voice Controlled Calculator
CalcTape - CalcTape is a revolutionary new kind of pocket calculator.