Best Slideshows with Jquery or mootools :

TripTracker : slideshow.triptracker.net
The TripTracker slideshow is a lightweight JavaScript image viewer with an animated slideshow feature – commercial

SmoothGallery : smoothgallery.jondesign.net
Using mootools v1.11, this javascript gallery and slideshow system allows you to have simple and smooth (cross-fading…) image galleries, slideshows, showcases and other cool stuff on your website – Free

GalleryView : spaceforaname.com/galleryview
GalleryView aims to provide jQuery users with a flexible, attractive content gallery that is both easy to implement and a snap to customize – Free

SlideViewer : gcmingati.net
SlideViewer is a lightweight (1.5Kb) jQuery plugin wich allows to instantly create an image gallery by writing just few lines of HTML such as an unordered list of images – Free

Flickrshow : flickrshow.com
Flickrshow is a lightweight, cross-browser javascript slideshow, providing you with an easy way to display your Flickr images on your own website. It is simple to install and can be used to access images within Flickr groups or photosets, or using a tag-based search – Free

Best Slideshows with Flash & XML :

Slideshowpro : slideshowpro.net
SlideShowPro is a Flash-based slideshow application for displaying photos and videos on any web site. Available as an ActionScript 2 & 3 component for Flash, as a gallery extension for Adobe Lightroom, and in standalone form for embedding yourself, SlideShowPro was built to meet the demands of photographers and web designers looking for an elegant, highly customizable utility for displaying slideshows without coding any ActionScript – commercial

dfgallery : dezinerfolio.com/2007/06/07/dfgallery/
As stated on many other articles on this site, dfGallery is one of the coolest Galleries currently on the Web. We have tested this gallery to the maximum but still having it in Alpha cos I am sure there will be a lot more feature additions. You could also request for a new feature on this Gallery by commenting below – Free

Flash Media Gallery : www.flashnifties.com
Flash image gallery, video gallery, mp3 music player, updatable flash website with an advanced navigation. It will then go through all the sub-folders and do the same, building a navigation with unlimited levels of sub-categories. Easily customisable through a simple text file with over 120 settings – commercial

TiltViewer : www.simpleviewer.net/tiltviewer
TiltViewer is a free, customizable 3D Flash image viewing application – Free & commercial (pro)