Author of a C++ calculator with a LaTeX syntax:

http://calculator-algebra.org

[double-click formulas to get their latex source].

Co-author and current maintainer of the freecalc project giving (free*) teaching slides from Precalculus all the way to Multivariable Calculus, and more.

*free = CC BY 3.0 unported

https://github.com/tmilev/freecalc