And here's a recent project just so this post will have something for the eyes...
My daughter was in this production. She loved every minute she worked with such a talented cast and crew. As a cast mom, I too had a blast. It was pure Joy. Another parent and I volunteered to be the "official" photographers. I created the photo collage in Photoshop CS2 and then sent the file out for offset printing onto 11x17 poster paper. The posters were sold as a fundraiser. This is most definitely a project that I do not regret giving my time to.
I made heavy use of the Place command, using it to add each photo as a smart object, so that I could manipulate them as much as I needed to until I was certain of their size and position. Another great thing about adding them as smart objects is that you can still edit the original file and have those changes automatically reflected back to your project. Say I found a flaw in an image, wanted to color correct it or remove that red scarf on the floor for example, I could double click the image in the layer palette, which would open up the original file for editing. Then save the changes back to the original file name and location and voila the changes are included in the placed layer.
Each layer also had a layer mask, so that I could re-edit the cropping with ease. Needles to say at one point it was a gigantic file that really taxed my system. It never got too big but if it did I could have just rasterized the layers I was least likely to want to change. I haven't actually counted but my best guess is there are more than 30 different images in this collage. [see the previous post for more on using the Place command and rasterizing]