For people who want to learn or teach mathematics on the basis of reason …
Ancillaries Management System
This is the system underlying the ancillaries of both Reasonable Basic Algebra v3-3 and Reasonable Algebraic Functions v4-1 which I am still testing. So, the sources are not yet on this site but the system itself is available here.
The system is described in an article which appeared in the PracTeX Journal on 2011-02-07.