What image slideshow applications have many transition effects?

Have you tried Shotwell (it is default in Ubuntu)?

And there is F-spot Photo Manager Click to install

F-Spot is a full-featured personal photo management application for the GNOME desktop. It simplifies digital photography by providing intuitive tools to help you share, touch-up, find and organize your images. It allows for importing of your existing photo collections, tagging photos with identifiers, as well as doing simple edits of photos (e.g. rotating).

And There is Picasa : Picasa Very well known and great image Application. Picasa slide show:

Take a look at Imagination. Its a DVD slide show maker featuring 69 transitions. I installed it from GetDeb.net.