Jim - An overview of Jim capabilities
SpeQ Mathematics - SpeQ is a small, extensive mathematics program with a simple, intuitive interface.
Insect - High precision scientific calculator with full support for physical units.
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.
errProof - The website has a lot of useful and unique tools.
NumWorks - The graphing calculator that makes learning math easier.