I'm not actually certain. Some of my cameras are still in storage. The ones I'm sure of:
Zeiss Super Ikonta B
Voigtlander Rollfilmkamera
RB67 (both 6x7 and 6x4.5 120 film magazines loaded)
Daiichi Zenobia
Kiev 4M
Rollei 35 (first version)
at least one of my Polaroid 600 family cameras
Ansco Shur-Shot Jr.
Also at least two of my 35 mm point-and-shoot models, one with corroded batteries that's going to be all kinds of fun to unload if I can't restore power.
I have loaded plate holders (9x12cm in film sheaths) for my Zeiss and Ica Ideal plate cameras, as well as several 4x5 holders for my Graphic View and Speed Graphic.
Some of these have been loaded since I closed down my old darkroom -- that was 2007.
I don't load film backs or cameras until I'm ready to shoot. I process almost immediately or ASAP after shooting. I use 3 frame auto bracketing when shooting slides with my F5. Result is I shoot "12 exposures of sorts"
Medium format, I get ready to go out, sometimes I load two different films with a couple backs.
1 Canon F1n with Koak Portra 400, 1 Canon F1n with Kodak Ektar 100, I Canon New F1-AE with Fuji 400X, 1 Canon New F1-AE with Agfa Precisa 100, and 1 Canon EF with Ilford HP4 Plus 400.
I generally don't load until I go out shooting, but (sort of half way there) I loaded three 8x10 film holders last night for today -- Worldwide Pinhole Photography Day! Unfortunately the day is utterly dreary and drizzly so maybe I'll try some indoor still life work.
Hmmm. Forgot it was WWPD. Might need to bring out my Ideal plate camera, put the pinhole shutter on it (because that's the only pinhole I know where to find on short notice, and I have some plate holders that have been loaded for more than a decade) and set up for a couple shots. Weather here is far from ideal, too -- overcast, though not actively raining at the moment -- but there is light, even if it isn't the best light.
The question made me think a bit... Some interesting answers.
I have a Retina IIIc, two Leicas, Hasselblad 500C, and Pentax Spotmatic loaded right now. There are rolls sitting in the bags, ready to load, in my Rolleiflex 3.5, and brand new Rolleiflex SL35, as well as my Super Ikonta. I think five loaded cameras is about my average.
Sixteen 8x10 film holders, loaded with HP5, FP4, Shanghai. Fifteen 4x5 holders, loaded with HP5, FP4, and remaining few sheets of Acros. One Holga loaded with HP5 120. One Holga Pinhole Wide loaded with Acros 120. Two RB67 magazines loaded with HP5, and Acros, respectively, One Ricoh 35, loaded with HP5. I'm locked and loaded but not stepping out as I've got too many negatives to proof from the past week... Curses!
Minolta Maxxum 650si + Sigma 24-50mm F4-5.6 + Kodak Max 800
I also have kinda of an odd point & shoot - it's a Kodak KZ3125, which is actually a Kodak-branded Vivitar PZ3125 with a Vivitar Series 1 lens. This is the only Kodak-branded P&S (Kodak slapping their name on another name brand) I can find. It's loaded with Fuji 200.
I have plenty of whole plate ready to load into holders for my 6.5 x 8.5 that I just put back into service this weekend. Ditto my 8x10 and some other smaller format cameras. I'll probably go out and burn some film through the whole plate this weekend coming up, or maybe after work one evening this week if I'm feeling exceptionally motivated.
Canon: EOS 3 (Ektachome), A2 (Portra 400), Rebel X (Gold 200), and A1 (Ultramax 400).
Lomography: Simple use reloadable (UFX 400) and LCA (HP5)
Bronica: 120 back (Delta 100), 120 back (UFX 100), 220 back (35mm Superia 400)
The Delta 100 was loaded back in Nov/Dec and the Ektachrome was loaded in Feb. Everything else was loaded since my quarantine started 44 days ago. Variety of color emulsions as my first C41 home developing was just a month ago and I'm trying a variety.
Just the three - some Delta 100 in my F-801s, Foma 100 in my Holga and ACROS 100 (the original stuff) in my Ondu 120 multiformat rise. Very restrained at the moment!
Let's see. 35mm: Nikon F5 and F6 are each loaded with E100G, and an F3P and F2AS are each loaded with HP5+,
120: Two A12 backs are loaded with PanF+, and three are loaded with E100.
On holidays this week, so I expect most of the film will be shot by Sunday...weather permitting.