We also have a digital camera that is used at the school as well as a camcorder, a polaroid and a regular film. They don't have to be checked out or in but so far, people have been very respectful and honest. However, this sounds like a good idea. Why wait for one to disappear!
We also have a problem keeping track of stuff when in our PTO cabinets. So, we have the school office (secretary) keep our camera - that way it is checked out. They like it that way too so they have ready access to it. We had no problems finding it this year by doing it that way (knock on wood). The pricinple could use it for an assembly if needed, or I could use it for an event at night, etc. We also have a ton of memory for it so we can get several hundred photos on it in very good quality (that was worth the extra $50 so we don't have to worry about it filling up). We spend about $300 total on the camera, memory and batteries. We made that money back this year on film and disposables that we purchased the years prior - and next year we won't have any investment in them.
Last school year we bought all of our teachers a disposable camera to use in the classroom and when they finished it we had doubles made. One copy went back to the teacher to use for her/his scrapbook or give to the kids and the other set went for use in the yearbook. It was a great way to get some of those "candid" shots of the kids working in the classroom that you don't always get to see in the yearbook pages.
We have 2 digital cameras, the kind with the disk and the kind with the cable (I know, I'm a technology genius ), they are supposed to be in a certian cabinet but where are they when the PTO wants one? No one knows! We bought them for the whole school to use and they are definately used. The 35 mm is supposed to stay in that cabinet too for such purposes but the 1 person in charge of the yearbook keeps it and will not let anyone else use it (that another story within itself).
We bought a digital camera this past year. We left it at thes school for them to take pitcures with whenever they had something (assemblies, lunch, recess, in classrooms) and also had it at all the events. It worked great for our newsletters and for the yearbook!
), they are supposed to be in a certian cabinet but where are they when the PTO wants one? No one knows! We bought them for the whole school to use and they are definately used. The 35 mm is supposed to stay in that cabinet too for such purposes but the 1 person in charge of the yearbook keeps it and will not let anyone else use it (that another story within itself). 
