Image Transition Manager with Scriptaculous and Prototype
I think the script works really great, you can have 8 (more to come) image transition effects to spice up your site. However, I found it a bit slow to load the image first time. It would be much better if the script preloads all the images beforehand.
Requirements: Scriptaculous 1.7.3 beta and Prototypejs 188.8.131.52 Framwork
License: License Free