Author of a C++ calculator with a LaTeX syntax:
[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
To check out our entire project:
svn checkout svn://svn.code.sf.net/p/freecalculus/code/trunk freecalculus-code