SpeQ Mathematics - SpeQ is a small, extensive mathematics program with a simple, intuitive interface.
MathCrunch - Learn math stress free
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.
Kalam Labs - Twitch for Science
NoteCalc - Browser-based notepad built for math calculations.
Fact Flow - Simple solution to help kids achieve math fluency