Jonah Bishop from Born Geek has an excellent tutorial that will help you create a Firefox Toolbar Extension using nothing but a bit of JavaScript, XML, CSS and a Zip utility!

If you’re writing AJAX code and/or standards-based web pages you should be using Joe Hewitt’s Firebug extension for Firefox. Version 0.4 has just been released and is the most significant upgrade to date. I have been beta testing this version for a couple of weeks now, and I can’t image developing without it. One of the greatest new features is a JavaScript Debugger that allows you to simply add breakpoints to your JS code, then step through your code line by line, and inspect local variables and the call stack. There are tonnes of other great features, so head over to Joe’s site and give Firebug a try!

From the creators of the fantastic Xyle Scope CSS debugging tool for OSX, comes a fantastic CSS 2.1 Reference. In my opinion this is the best reference available online. It’s very well organized and the interface is very snappy.

Yahoo! UI Library is now offering a collection of seven web page templates that generate Grids CSS. The templates offer the the ability to nest grids of one to four columns within the content area of those templates. This provides you with more than 100 page layouts with a single CSS file at just 1.82KB. The templates and CSS have A-Grade browser support and many other great options!

The Particletree blog has a nice article titled - A Designer’s Guide to Prototyping Ajax - that walks you through a suggested process for developing prototypes of these new fandanagled web applictions. The article focuses on creating good wireframes using standards compliant XHTML and CSS.

Spiffy Corners is a CSS technique for making anti-aliased rounded corners on your HTML boxes.  The result is very nice considering the solution uses no images or JavaScript.

Bubble Tooltips is some more CSS magic from Alessandro Fulciniti that creates some very nice Javascript and CSS based tooltips.  As with other scripts from Alessandro, this one uses unobtrusive Javascript and degrades perfectly!

Quick Lookup is simply the most amazing web programming reference I have come across in quite a long time.  It is an AJAX enabled tool that allows for quick lookup of syntax for PHP, MySQL, JavaScript and CSS.  You can load it into your sidebar for easy access.

Roger Johansson from 456 Berea St continues to impress with his latest article titled CSS 3 selectors explained. He covers the new selectors that allow you to match patterns in attribute values and a whole slew of new pseduo-class selectors.

Another advent calendar worth reading is 24 ways. Again a post every day from December 1 to December 24 except this calendar post totally awesome general web development tutorials.