The calculus tutorial is going great! I decided that tangent lines was not the best subject to start with, so now the order is limits -> continuity -> one-sided limits -> limits at infinity -> tangent lines, with an optional pre-calculus and trigonometry review at the start. I keep a live mirror of the tutorial on sage.math at this link:
Do take a look! And if you have any feedback or suggestions, too, let me know at firstname.lastname@example.org or email@example.com, as I would love to hear your input.