Popular photo sharing site Flickr has published lists and graphs of the most popular cameras used on the site.
The results are an incredible camera guide. Not only can you see the most popular cameras overall, as well as most popular point and shoot cameras and cameraphones, but you can check out pictures taken with each camera for an idea of what kind of shots the camera is capable of taking. On the individual camera page, Flickr displays a graph of that cameras usage, which should give you a good view of whether or not it's going out of style. Naturally, you can also compare prices at Yahoo! Shopping if you find a camera you're interested in.
A couple of months back, Yahoo! Shopping posted the top 10 Flickr cameras - which was great, except that they're mostly high-end cameras. The new Flickr camera guide runs the gamut, and should be a great resource if you're planning to buy a new digital camera this holiday season.