Quicksolve is an interactive graphing calculator and programming language. It provides an intuitive interface for performing basic plots and calculations with a focus on numerical solutions. Versions will be available for both Gnome and Mac OS X.
QPlot - an Advanced Mathematical Calculator
Includes: natural-style input, 2-D and 3-D graphing,
differentiating, integrating, equation solving, C-like
PROGRAMMING, and a lot more!
What's most exciting, it is EXTENSIBLE!