EfectoHD shares his process and project files for making a slideshow of photos without keyframes in After Effects:
"More than a tutorial, this is the explanation of a technique that I can be of use when creating these slideshows easy in After Effects without creating not a single keyframe.The technique involves creating a series of zero, each with a basic motion: zoom in, zoom out, panning left, panning right ... all with a constant speed then we will provide a basis to encourage the photos." ...via Lester Banks.
For other options on slideshows, click the tag slideshow, which includes an After Effects tutorial by Lloyd Alvarez at AEtuts, Create A Rockin’ Automated Slideshow and the Video Copilot tutorial 12. Elegant Slideshows. See also a Simple gallery in 3D not using the cylinder effect-- Tutorial After Effects by "The Great Zimm."