Boston.com's The Big Picture is what I feel, at the moment, one of the best photo essay webpage. The webpage features nothing but big pictures with short captions. The latest Olympics series of photos has just garnered over 500 comments in 2 days. The number of views must be staggering. That particular page has also been submitted to digg.com, with 1600 over votes.
It's really a great concept that any newspaper could have easily done using wired photos.
There's an interview with the creator, Alan Taylor. It's well worth the read.
I was looking around a forum when a thread with the title "Awesome pics from the Olympics Opening Ceremony". My mind immediately connected with The Big Picture, and sure enough, inside was a link to that page.