From a tutorial on building an RSS SAX parser on my website:

full article can be found here

Function that you can use to extract the ID from YouTube links that
look like this:

http://www.youtube.com/watch?v=Fv2aS8YtpmU
http://www.youtube.com/vi/Fv2aS8YtpmU
http://www.youtube.com/?v=Fv2aS8YtpmU

and you can extract this "Fv2aS8YtpmU" so you can use it to get thumbnails that look like : http://img.youtube.com/vi/[videoid]/default.jpg

libNog is a 9k library to provide somewhat easier browser-independence. It is not yet complete, and will be continuously revised. It grew from this snippet, and is still growing as I find things I use often.
Presently, libNog features:

A way to browser-independently get an XMLHttpRequest object.
A set of simple methods for GET, POST, HEAD, and to include other Scripts.
Simple methods for className control
A completely abstracted form of getElement*
Browser-independent methods for attaching and detaching event handlers
An event-normalization routine
A simple one-command 'Stop the Event' routine
And the big one: A simplified Class object by which classes can be built in JavaScript.

I use something similar to this in an application named Shock 3. It provides you with your own Custom settings that can handle your own Custom types as well.

This is a brief revision to my previous snippet. It is still what it was: a small, simple system for using XMLHttpRequest without using globals.

I'll put the API spec in the code this time, so as not to clutter the front page further.

Changes:

Changed name to HTTPRequest (far more accurate)
Added HEAD requests
Shortened code by making a GenericRequest function
Used a better method for getting an XMLHttpRequest object (checks multiple MS versions and implements the latest one)

This is a simple script to provide basic cross-platform XML request functionality in Javascript. It's meant to be the core component in any AJAX style framework. It is not an instantiable object, but instead is a namespaced microlibrary.

Calling is easy:
XMLRequest.GET(uri, query, callback, fallback)
uri: The location you're after
query: an associative array of form data to provide via the URL
callback: callback function of the form myCallbackFunction(objXMLHttpRequest), which is called upon successful (response = 200 OK) retrieval of the XML data
fallback: myFallbackFunction(objXMLHttpRequest), which is called upon failed (response != 200 OK) retrieval of the XML data.

XMLRequest.POST(uri, query, form, callback, fallback)
Similar, but does the query using the POST method. 'query' is the URL-appended data, still in associative array form, and 'form' is the same for the POST data.

This code illustrates using ruby REXML package. It converts J2EE web application deployment descriptor web.xml into Freemind mindmap document.

Implementation-independent XML builder.

This function converts a CSV file to a simple XML file.

I've seen XML 2 Array functions done in other ways but this is the shortest implementation I've seen yet. I didnt write it myself though, but I thought I'd submit it for common good of this site. It uses regex and works prefectly.

Retrieve information about a file

Transform XML File with XSL Stylesheet