Teaching the major heresies and the problems with them directly also is valuable. A course in apologetics with heresies/cults as a focus will give people the tools to speak to anyone being sucked into a cult.
Heresies then and now: ancient Christian heresies practiced in modern times
The Rev. John Piper: an interesting look at "heresy vs. schism"
Pietism as an Ecclesiological Heresy
Arian Heresy Still Tempts, Says Cardinal Bertone (Mentions Pelagianism As Well)
Catholic Discussion] Church group stays faithful (to heresy!)
Where heresy and dissent abound [Minnesota]
Gnostic Gospels - the heresy entitled "Gnosticism."
The So-Called ‘Gospel’ of Judas: Unmasking an Ancient Heresy