Texrat: I've often wondered about that, too. Why isn't there any standardised slideshow "playlist" format? You would want a list of photos, length of time to show each photo, and optionally, the transition to use between photos. Never seen anything like that.

EDIT: I don't mean software that makes a slideshow into a video or something. I mean a meta-file that doesn't contain the actual media, just information about how to present it in a standardised format that any slideshow app can read.