If you mean a panorama, most modern cameras have a setting for that, when I found the one on my parents camera I went crazy! If you mean like scrapbook style there are plenty of websites for that. If you mean a photo inside a photo, like photoception then I find the easiest thing to do is first take the photo that you wanted nested and print it and then take the second photo with the original one in it! Hope this helps!!
If you're talking about Photoshop and making a panorama, expand the canvas size by 500% (Image->Canvas Size, then change it to "Percent" and check the "Relative" box), then drag the photos all into that one .psd. Or I missed the point of your question.