Here is collection of exiting and useful jQuery Scripts and Plugins.
Jcrop is the quick and easy way to add image cropping functionality to your web application. It combines the ease-of-use of a typical jQuery plugin with a powerful cross-platform DHTML cropping engine that is faithful to familiar desktop graphics applications.
Apply Dropshadow effect to fonts, inputbox, images and Block tags using jQuery.
Captify is a plugin for jQuery written by Brian Reavis to display simple, pretty image captions that appear on rollover. It has been tested on Firefox, Chrome, Safari, and the wretched Internet Explorer. Captify was inspired by ImageCaptions, another jQuery plugin for displaying captions like these.
This collapsible breadcrumb was developed to deal with deeply nested, verbosely named pages. Rather than limit the amount of elements shown on the sever side, we decided to go with a client side solution for usability and SEO reasons. It also turned out nice to look at and fun to play with.