Tinycon allows the addition of alert bubbles and changing the favicon image. Tinycon gracefully falls back to a number in title approach for browsers that don't support canvas or dynamic favicons.
Alerts in the favicon allow users to pin a tab and easily see if their attention is needed.

An extremely useful library for generating data. Great for testing?

A simple, micro event dispatching library for PHP

Symfony2 Security component for handling auth/entication+risation

I can use this to find some research areas to study in

A general purpose Python data validator

grumble.js provides special tooltips without the usual limitations of north/east/south/west positioning.

Customisable "loading" spinner animation in Javascript.

Port of the Underscore.js library to PHP

Nice library for logging

Very nice map library. Very very nice. It doesn't do a lot but but it does it well. Curly's Law at it's finest.

The HEAD section is the worst place to load scripts. It's painfully slow. The more and the bigger the worse it gets. Move scrips to the bottom and you run into dependency issues and you cannot safely use HTML5 and CSS3. Enter Head JS. A compact solution to these universal issues. 

I was looking at Idiorm a while ago, and it seems its back and it brought a friend!

Markdown for C#

Looks great for a little project involving web comics that I've always wanted to do. Will have a look see :)

Docsplit is a command-line utility and Ruby library for splitting apart documents into their component parts: searchable UTF-8 plain text via OCR if necessary, page images or thumbnails in any format, PDFs, single pages, and document metadata (title, author, number of pages...)

A *better* Mustache templating library for JavaScript

A large library for wireframing user interfaces in Adobe Ilustrator. This is Most Excellent Dude.

Polymaps. Absurdly classy: “a JavaScript library for image- and vector-tiled maps using SVG”. It can pull in image tiles from sources such as OpenStreetMap, then overlay SVG paths specified using GeoJSON. The demos make use of GeoJSON tiles for US states and counties hosted on AppEngine. The library is developed by Stamen and SimpleGeo, and released under a BSD license. SVG support in the browser is required.

I really like how this looks, and feels. Some beautiful neat looking code.

I like

I think I just like Lithium

I think I like how their Data class is designed.

This looks like absolutely delightful form validation plugin for jQuery.

API Documentation for web.py

JavaScript library for creating tool tips

This looks like it would be good for making a Tree class in PHP simpler :)

A very lightweight PHP framework inspired by Ruby's Sinatra and Camping, and tiny micro frameworks in general. I like!

OCR for Python. :)

Template engine for Python; heavily inspired by Django's template engine.

Thematic mapping library for Google Map

A library for doing inflection type stuff, pluralisation, capitalisation etc.

phMagick is wrapper for ImageMagick written in php 5. This is made of awesome.

An example of a nice design/ui patterns library for an app/organisation.

A PHP DOM API based on jQuery (Sizzle?) like CSS3 selectors.

Library for parsing CLI options

A pretty neat DAL(Data Access Library) for .NET

A list of API/wrappers for using SQLite in different languages. C#.NET included :)

Datejs is an open source JavaScript Date library for parsing, formatting and processing. Comprehensive, yet simple, stealthy and fast. Datejs has passed all trials and is ready to strike. Datejs doesn’t just parse strings, it slices them cleanly in two.

MySQL ADO.Net provider for the .NET framework :)

A CSS selector library for Javascript. Its small and zippy, it can be dropped in anywhere, and overall just good stuff. Its used by jQuery. Comes in really handy when you want to select elements easily, but don't jQuery overhead.

An excellent little debugging tool for PHP. Outputs debug information in a nice easily styled table. Perfect for quick peeks at your variables.

PHP_CodeSniffer is a PHP5 script that tokenises and "sniffs" PHP, JavaScript and CSS files to detect violations of a defined coding standard. It is an essential development tool that ensures your code remains clean and consistent. It can also help prevent some common semantic errors made by developers.

You can get the elusive pre-built JPEGTran binary for Windows here. Just need to peruse the page. If you don't want to snoop, the link is: http://sylvana.net/jpegcrop/jpegtran/jpegtran.exe and http://sylvana.net/jpegcrop/jpegtran/jpegtran.zip at time of bookmarking.

Whoosh is a fast, featureful full-text indexing and searching library implemented in pure Python.

Hypy is a fulltext search interface for Python applications. Use it to index and search your documents from Python code.

Forget ORM, this is way cool.

This looks to be a really nice and light ORM framework for PHP. I think I shall use it in my next project. Did I mention it looks simple and dead easy to use?

A collection of interaction and interface patterns. :)

Some of the basic interfaces you can implement in PHP. Don't quite think these are 'Standard Libary' but, just grouping them together for easy reference.

Fluent interfaces, method chaining and all that good stuff.

Some more props and praise and information about the goodness to be found in the PHP Standard Library.

A PHP extensions that provides a bit more debugging information about your scripts than you'd get normally.

A nice article showing how to extend some of the interfaces in the PHP standard library to be able to treat some of your classes as arrays etc. Really useful stuff. :)

A caching library for PHP

HTML Purifier is a standards-compliant
HTML filter library written in
PHP. HTML Purifier will not only remove all malicious
code (better known as XSS) with a thoroughly audited,
secure yet permissive whitelist,
it will also make sure your documents are
standards compliant, something only achievable with a
comprehensive knowledge of W3C's specifications.
Tired of using BBCode due to the current landscape of deficient or
insecure HTML filters? Have a
WYSIWYG editor but never been able to use it? Looking
for high-quality, standards-compliant, open-source components for that
application you're building? HTML Purifier is for you!

Minify is a PHP5 app that can combine multiple CSS or Javascript files, compress their contents (i.e. removal of unnecessary whitespace/comments), and serve the results with HTTP encoding (gzip/deflate) and headers that allow optimal client-side caching. This helps you follow several of Yahoo!'s Rules for High Performance Web Sites.

Handy collection of tools, including some nice charting apps. No idea why, but charting libraries are getting my attention nowadays.

A collection of useful libraries and screencasts for CodeIgniter, the PHP framework