Panoramio has now more than 2 million photos online (October 10th, 2006 there was 50,000) . When you are browsing around Google Earth and Google Maps you may seen little pics of the areas that you are looking at and most of these come from Panoramio. Panoramio allows users to upload their photos and then these photos can be (if liked) included in the Google index.
I personally have two photos included - one from Dubrovnik in Croatia and another from the Moroccan Desert.
http://www.panoramio.com/user/1946508
I had not been to the site for a month or two and noticed that they had a new feature called Look Around. This allows you to see other peoples photos of the same location as your photos or the photos you are looking at and it is amazing. Microsoft has done a lot of research into a similar project (which is now live) which is called PhotoSynth - http://livelabs.com/photosynth/ but that project goes well beyond this and is absolutely amazing in its own right.
I live in Christchurch, New Zealand and in the centre of the city we have a Cathedral. Clicking on the link below will open this up and you will be able to see other peoples photos which include the Cathedral with smooth transitions between the different users photos.
Christchurch Cathedral
http://nv0.panoramio.com/navigate.php?id=573765
Dubrovnik, Croatia
http://nv0.panoramio.com/navigate.php?id=11680114
Check it out at http://www.panoramio.com/ and they also have an API so you can display photos from Panoramio on your own web site http://www.panoramio.com/api/