I think the latest top end canon was using a new raw where it saved like 40 different layers to be processed later. I've never really done much with the raw files even though I shoot jpg+raw.
A few cameras offer composite modes now. Pentax and Oly shift the sensor a pixel width for four shots and combine into one for an extremely large, high detail shot. You get full colour sampling at each pixel location instead of just one. It can also result in much less noise since the layers can ditch the noise from each and choose the detail layer for any given pixel.
The big caveat is that any movement whatsover, be it subject or camera, will result in strange artifacts in the image. Pentax claim that theirs can account for some movement but in practice its still problematic. And your lenses need to be top shelf.
Oly also have what they call "live composite", where you can take interval shots and it will blend them together but only use changes in brightness relative to the base shot. It gives an effect like using an ND filter for water movement, for instance. Or a really strange but kinda cool thing where you can take a pic inside a crowded area and gradually all the people moving through the shot will be composited out of the pic and you're left with just the stationary building etc. I saw one inside Grand Central Station that seemed totally empty despite being continuously crossed by commuters. Cant quite get my head around how that works, lol.
I havent yet used these modes on my new Olympus. But i agree with Deck. I can mainly envisage "artsy" use. Maybe astrophotography as well.