I've always been a huge fan of the Magnum In Motion site.
They have some great mini-documentaries, in really nice, elegant, Flash wrappers.
The 'Essays' section gives us the opportunity to hear the photographers who took the shots, give the background to them, which makes for a richer experience.
The Observer is doing similar which is great too, and they've cleverly added something that I don't think Magnum have, which is a roll-over drop-down on each shot with additional textural info. Very neat.
(You can also subscribe to the essays on iTunes but the picture quality is poor compared to the main site.)
(Oh, and on iTunes, it's sponsored by Nokia with fairly modest 15 second ad on the opening titles. Which is okay in my book.)
And of course, why stop at photo collectives and newspapers?
This rich slideshow technique would work just as well for advertisers.
Not just for front-end sponsorship like Nokia, but with brands embedded in the fabric of story.
For example a reportage photographer might cover how people use cash machines for bank for, with audio interviews/observations/piss-takes, whatever. A photographer/soundrecordist might tag along on a book tour with a famous author, or a stag weekend sponsored by a beer company, or one of those 'Day in the life of a brand' pieces; you get the idea.
I also think that good stills slideshows online, with great sound, often have the edge over crappily encoded full motion video. You kind of 'get more out' of static images that 'token' video.
And of course, 'civilians' could use it too:
Imagine a Flickr extension, whereby you could add a sound track to the existing slideshow function, integrating with Odeo or something, or from your mobile phone from the gig, the holiday, the presentation/conference whatever.