A thought-provoking Newsweek article: "Is Photography Dead?" There's also a thread on the DPC forums discussing the article and ideas.
You know, the best part about the web is the ability to look up many famous photographs, especially using Google Images. For instance, the image above from The Art of the American Snapshot 1888-1978 is referenced in the article but not shown. A quick google images search brings it up though. Likewise, if you are unfamiliar with Cindy Sherman, as I was, you can search for her images.
Also notable (from the DPC thread): Eric Baudelaire's Dreadful Details. Take the time to figure out why and how the photo was made -- you won't be disappointed.