Countdown.js is a JavaScript library for calculating and displaying the timespan between two dates.

The library calculates the value continuously considering "the time goes on" and keeps generating an accurate output.

It can provide the timespan in many formats like milliseconds, seconds, minutes, hours, days, weeks and even millennias.

There are methods for displaying it as an English sentence like "3 years, 6 months, 21 days, 10 hours, and 32 minutes".

The countdown can be reset easily and there are callbacks both on start and end.

DOM Monster is a bookmarklet, created by Thomas Fuchs of script.aculo.us, for analyzing the DOM and several other features of a page.

It works cross-platform/browser, checks the HTML + JavaScript codes and can come with warnings/suggestions like:

• Reduce the number of tags that use the style attribute (85 elements)
• Found 16 JavaScript globals. Reducing them can increase performance
• and more..

The bookmarklet is not an all-in-one solution, however, can be used side-to-side with other tools like Firebug, PageSpeed, YSlow, etc.

Also, it is open source and can be improved/customized further.

jqPagination is a jQuery plugin for quickly creating a JavaScript-controlled pagination interface and functionality.

The plugin is controlled with the special class names and attributes of HTML elements (for defining the prev, next buttons or setting the max pages).

It has a pretty unique, simple-yet-functional feature which is the ability to clicking on the pagination item and setting the page to be displayed manually.

jqPagination has a single callback which is ran when a pagination request is made and returns the page number to be displayed.

Its design can be customized easily and the plugin degrades nicely when JavaScript is disabled.

Sometimes, we need to display images that are bigger than the viewport or we have a limited space.

PanoJS3 is a JavaScript widget that stitches together a set of tiled images and presents it with panning + zooming support.

It is a very useful widget specially for displaying panoramic images, maps or huge documents.

Besides the desktop, it also works on mobile browsers with touch interfaces (supports pinch to zoom and pan gestures).

A simple map helps finding out the which part of the image is being viewed and it is possible to enable fullscreen mode with a click.

IM.js is a JavaScript library that can find the differences between images very quickly.

It scans the given images pixel-by-pixel using HTML5 canvas and outputs their similarity ratios.

The developer has created IM.js for auto-testing the similarity of URL snapshots taken from different browsers which is a great idea for quickly finding out any rendering differences or problems. It can also be used for many other cases like detecting duplicate images.

And, besides the ratio, it can create a canvas where the two different images are joined for easily seeing the differences at one sight.

CSS transitions and transforms provide a wide range possibilities for animating and morphing HTML elements.

If you would like to use them inside jQuery, jQuery Transit reaches to the rescue.

It is a plugin for implementing CSS transitions and transforms, has the same syntax as .animate, supports most of the methods and has the jQuery juice like callbacks, chaining, auto-browser-prefixes and more.

The plugin uses jQuery’s effect queue by default, so, transitions will never run in parallel.

It doesn't offer compatibility with older browser versions as real CSS3 rules are applied (rather than .animate) but degrades nicely and/or you easily force it to siwtch to the frame-based animation.

Moments.js is a feature-rich JavaScript library for working with dates (parsing, manipulating, and formatting them).

It works both in the browser and server with NodeJS as all code is compatible with both of the environments.

The library can easily convert any given date to many different formats, add/subtract dates, hours, etc. and has methods for displaying user-friendly date/times like "in 5 days"

Moment.js is multilanguage and any new languages can be easily added by editing a language file.

Validate.js is a very nice JavaScript form validation library that is inspired from the CodeIgniter form validation API.

The library is lightweight (~1kb gzipped), doesn't require any JavaScript frameworks and works in all major browsers (yes, including IE6).

Validation rules that are used frequently like numeric, required, e-mail, less/greater than, etc. are already included and it can be extended with new, custom rules.

It has support for chainable declarations for easily using multiple rules on a single input field.

And, although there are hard-coded warning messages for each rule, they can be overridden with a method provided.

Lungo.js a framework, powered with HTML5, CSS3 and JavaScript, for creating mobile web apps.

The applications created with it works in all of the popular platforms (iOS, Android, Blackberry and WebOs).

It has support for touch events like tap, double-tap or swipe and doesn't use images (including the icons) as everything is vectorized.

HTML5 features like WebSQL, geolocation, history or device orientation can all be used.

A well-documented JavaScript API has methods for handling all the major stuff and Lungo.js is modular + completely customizable.

Minimit is a very flexible jQuery plugin for creating any type of content sliders including galleries, slideshows or carousels.

It is good fit for designers/developers who wants to build completely custom outputs as the plugin covers all the logic required but asks you to to code all the animations and the CSS.

The plugin has a good number of options that control the interactions and callbacks exist on every level.

Minimit has a documentation page and a list of demo sliders that show how powerful it can be.