Here are 10 Cool jQuery Progress Bar Plugins to indicate to user that something happens and when it will be approximately done.

Percentage Loader

A tiny jQuery plugin for displaying progress in a visual and engaging way.

progression

A jQuery plugin that gives users real time hints & progress updates as they complete forms.

Presentation Cycle

Presentation Cycle is a variation on the functionality of Cycle. Instead of generating a list of numbers that are clickable Presentation Cycle generates a progress bar that shows when the new slide will appear.

TRNSFR

TRNSFR is a UI element meant to be used in conjunction with your current upload script.

jQuery Knob

This looks like a handy jQuery plugin for making circular progress bars, knobs, etc.

Animated jQuery Progressbar Plugin

You’ll learn how to expand possibilities of jQuery widget – Progressbar.

jQuery File Upload

File Upload widget with multiple file selection, drag&drop support, progress bars, validation and preview images, audio and video for jQuery.
Supports cross-domain, chunked and resumable file uploads and client-side image resizing.

Beautiful CSS3 And JQuery progress bar

Fancy progress bar using CSS3 and jQuery, but no Flash or even images.

CProgress

jQuery circular progress bar.

jqBar

Simple jQuery plugin for creating animated vertical and horizontal bars. The plugin is called jqBar. jqBar can be used in variety of situations where you want to present data with some visual effects. It helps you crate beautiful bar charts to represent skill set or can be used as a progress bar. Plugin is very light weight and can be completely customized.