Have you ever waited patiently in front of a landmark, maybe a fountain or cathedral, hoping that there would be a magic moment when there was no one in the frame--no dogs, no kids, no tourists taking their own pictures?
I've spent many such moments, not always patiently. Sometimes I would give up, other times the image wouldn't be what I wanted because I needed to snap away in the .5 seconds when the coast was clear.
I have discovered an almost unbelievable function in Photoshop: the ability to combine multiple photos and create a composite in which there are no people (or dogs). To do this, you need to take several pictures of your subject. It doesn't matter how many people are in them, as long as there are at least two shots showing each part of the landmark (in other words, there need to be at least two shots in which no one is standing in front of any particular point). Once you get back to your computer, fire up PS, align the layers, and voila--a clean image.
There are a couple catches. First, I believe you need the extended version of PS to do this. Second, the first time around, it's a little tricky (at least for me) to sort out all the steps. However, once you get the hang of it, it's a piece of cake. Just look in PS help under 'align layers.'