The first website's photo slide shows I tried was MSNBC.com's.
They were what I expected: functional.
There was plenty of historical context given in each caption, the photos were numbers and they were navigated with ease. Basically,there were no flaws but it didn't do anything that blew me away. There was a GIANT spam advertising logo at the bottom, though.
Next, I tried Reuters.
Functionally, it was a little harder to navigate than the last one I tried. But, it was not that bad. There were no advertisements, but there was the option to "buy" the particular print. One cool feature was the "best photos of the week" option. The captions explained the context and it gave a good visual representation of the week's news.
Finally, I tried Time's.
Unlike the other's, there was no box that popped up from the website, the slide show functioned within the actual site. This was different, and neither detracted from or added to the experience. The captions were too vague, but the ideas for the shows were inspired. For example, there was the depressing/captivating "Trader's Faces" show which depicted the near-suicide expressions on Wall St. traders from the past week.