I, like Tan, have a fascination for 8 day movements so the 8 day reference thread on the old HF was one of my favorites.
Let me start a new one here, and I hope that others will add information when they can...
(size format is: overall diameter / thickness (in mm))
Felsa cal. 4100
30.9 / 4.5
Found in Crestwood, Baylor and some other 8 day wristwatches
A.Michel cal.50
28.5x23.4/5.1
Probably smallest 8 day vintage movement.
Lemania
31.8 / 6.7
Juvenia (A.Douard?)
33.4 / 6
Angelus cal. SF-N 9 (tentative cal no, according to this)
32x21.5 / ? (I haven't measured the thickness yet)
Hebdomas
42.2 / 10.4
Probably the most popular vintage 8 day movement. Sometimes they are found of the smaller size (~35mm?), but this one is most popular. As usual for Hebdo balance is on the dial side, although sometimes it's fully covered by the dial (like it was on in this one)...
LeCoultre
43.0 / 5.3
LeCoultre has made a few of 8 day movements, but this one is the most good looking
Movado 310M
43.2 / 8.6
Very weird inscription on this one: 15 jewels, 2 substitutes for jewels
Wasner et Fills, Besancon (French, not swiss made)
45.0 / 7.2
This particular movement has no markings.
It has oversized main plate - I've seen these for sale with the mainplate of the more usual size (~43mm).
Mathey-Tissot alarm (A.Schild cal, but I forgot the no
)47.5 / 10.7
Size is overall, but the movement has an additional plate mounted on the mainplate, which houses some of alarm parts - without that, it's ~42-43mm dia.
Octava
54.2 / 10.5
This particular is 24 lignes, but they were made in 19 ligne size too. Usually they are marked Octava, rarely are sterile. These movements were used by Rolex for their travel clocks.
Waltham 37 size
61.2 / 13.1
Probably the biggest "watch style" movement that I know of
