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
I thought of this scripture as I went through some of the heresy threads you pointed to:
Revelation 2
To the church in Ephesus
1”To the angel[a] of the church in Ephesus write:
These are the words of him who holds the seven stars in his right hand and walks among the seven golden lampstands: 2I know your deeds, your hard work and your perseverance. I know that you cannot tolerate wicked men, that you have tested those who claim to be apostles but are not, and have found them false. 3You have persevered and have endured hardships for my name, and have not grown weary. 4Yet I hold this against you: You have forsaken your first love. 5Remember the height from which you have fallen! Repent and do the things you did at first. If you do not repent, I will come to you and remove your lampstand from its place. 6But you have this in your favor: You hate the practices of the Nicolaitans, which I also hate. 7He who has an ear, let him hear what the Spirit says to the churches. To him who overcomes, I will give the right to eat from the tree of life, which is in the paradise of God.