Checkpoints in New Testament Canonization

Here is a short, simple summary of checkpoints in the canonization process of the New Testament.

AD 50 - AD 95 The authors themselves
New Testament authors knew they were writing authoritative Scripture and also quoted other parts of the New Testament as authoritative Scripture. Churches were circulating these books although no one seemed to have thought of making an authorized list of books.

AD 110 Ignatius of Antioch and Polycarp of Smyrna
These immediate disciples of the apostles wrote letters (Ignatius 7, Polycarp 1) with quotations from the New Testament.

AD 140  Marcion's truncated New Testament canon
Marcion of Sinope, founded a heretical sect and produced a list of accepted (which he used to support his doctrine) and rejected  New Testament books. In doing so, he kind of listed the New Testament books in circulation during his time.
Accepted - Luke Galatians 1Corinthians 2Corinthians Romans 1Thessalonians 2Thessalonians Ephesians (which Marcion called Laodiceans) Colossians Philemon Philippians
Rejected - Matthew John

AD 180 Muratorian fragment
The Muratorian Canon (also called the Muratorian Fragment) is an ancient list of New Testament books - the oldest such list found. The original document, which was probably written in Greek, is dated to about AD 180 and lists 22 of the 27 books of the New Testament.
Includes - Four gospels, Acts, 13 Pauline Epistles (exclude Hebrews), 1John and one more (not sure 2John or 3John) Jude, Revelation, Wisdom of Solomon
Omits - Hebrews, James, 1Peter, 2Peter, 2John or 3John

AD 322 Eusebius of Cæsaria
Eusebius's Ecclesiastical History 3.25.1-7 has 4 lists:
1. accepted works - 4 gospels, Acts, 14 Pauline letters, 1Peter, 1John, Revelation, total 22 books
2. disputed works - James, Jude, 2Peter, 2John, 3John
3. rejected works - Revelation (but it was on the accepted list)
4. heretical works - did not contain any works now regarded as part of the New Testament

AD 367 Athanasius of Alexandria
Athanasius's 39th Festal Letter listed the complete New Testament canon (27 books) for the first time.

A more detailed reference can be found in The Development of the Canon of the New Testament - Cross Reference Table Writings and Authorities and The Development of the Canon of the New Testament.