A simple but good carousel, if you just need the basic effects.
Its developed using YUI(Yahoo User Interface) and is semantically coded.
Inspired by the carousel you can see on panic.com, here is Glider, a Prototype based slideshow. A really cool use of Glider has been done on the amazing WP Magazine Theme for Wordpress.
jCarousel is a jQuery plugin for controlling a list of items in horizontal or vertical order. The items, which can be static HTML content or loaded with or without AJAX, can be scrolled back and forth with or without animation.
The jQuery Multimedia Portfolio will automatically detect the extension of each media and apply the adapted player. Play multimedia files in style with the cool jQuery Multimedia Portfolio.
Using mootools, SmoothGallery 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. 
Noobslide is a Mootools slider plugin. Noobslide allows numerous variations and customization, despite of its lack of offical documentation.
SpaceGallery is a new JQuery plugin that provides smoky out of the fantasy effect to images. Bring in a smooth slidinf effect to image views with this wonderful javascript slider.
Christmas is a season to showcase your creativity and best designing skills. This collection of JavaScript christmas effects tutorials cover addition of christmas lights, colorful santaclause, generation of christmas trees for websites and much more. Decorate your website with a christmas theme using these colorful JavaScript effects.
Every Christmas tree needs flashing lights – and with Javascript that Christmas tree and its decorations can be on a web site.
