Tatsuhiko Miyagawa's blog

Another example of what’s getting extraordinarily popular in Japan: Programming Advent Calendars.

• a-blog cms Advent Calendar 2011
• Android Advent Calendar 2011
• 日本App Inventorユーザー会 Advent Calendar 2011
• Backbone.js Advent Calendar 2011
• bjam Advent Calendar jp 2011
• Boost Advent Calender 2011
• C# Advent Calendar 2011
• C++11 Advent Calendar 2011
• CakePHP Advent Calendar 2011
• Clojure Advent Calendar 2011
• Cloud Foundry jp Advent Calendar 2011
• cocos2d Advent Calendar 2011
• Competitive Programming Advent Calendar
• DevLOVE 4tate Advent Calendar 2011
• Dvorak Advent Calendar 2011
• Emacs Advent Calendar jp: 2011
• Esolang Advent Calendar 2011
• F# Advent Calendar 2011
• FuelPHP Advent Calendar 2011
• Functional Ikamusume Advent Calendar jp 2011
• G* Advent Calendar 2011
• hadoopアドベントカレンダー2011
• Haskell Advent Calendar 2011
• HTML5 Advent Calendar 2011
• iOS Advent Calendar 2011
• Java Advent Calendar 2011
• JavaScript Advent Calendar 2011 (Node.js/WebSocketsコース)
• JavaScript Advent Calendar 2011 (WebGLコース)
• JavaScript Advent Calendar 2011 (オレ標準コース)
• JavaScript Advent Calendar 2011 (フレームワークコース)
• Jenkins Advent Calendar jp 2011
• KINECT SDK Advent Calendar 2011
• Less & Sass Advent calendar 2011
• Mac Dev JP advent calendar
• Mercurial Advent Calender 2011
• MySQL Casual Advent Calendar 2011
• Nimrod Advent Calendar jp: 2011
• OpenNI Advent Calendar 2011
• Perl6 Advent Calendar 2011
• Perl Advent Calendar Japan 2011 - Acme Trap
• Perl Advent Calendar Japan 2011 - Casual Track
• Perl Advent Calendar Japan 2011 - DBIx Track
• Perl Advent Calendar Japan 2011 - English Track
• Perl Advent Calendar Japan 2011 - Hacker Track
• Perl Advent Calendar Japan 2011 - Test Track
• PHP Advent Calendar jp 2011
• PHP5.4 Advent Calendar 2011
• Play! framework Advent Calendar 2011 jp
• Plone 4 Advent Calendar 2011
• PostgtreSQL Advent Calendar
• PowerShell Advent Calendar 2011
• Processing Advent Calendar 2011
• PyPy Advent Calendar 2011
• 2011 Pythonアドベントカレンダー(Python3)
• R Advent Calendar 2011
• Ruby Advent Calendar jp: 2011
• Scala Advent Calendar jp 2011
• Silverlight Advent Calendar 2011
• Software Test ＆ Quality Advent Calendar 2011
• Symfony Advent Calendar JP 2011
• TDD Advent Calendar jp: 2011
• TFS Advent Calendar
• Theorem Proving Advent Calendar
• Titanium Advent Calendar 2011
• Vim Advent Calendar 2011
• Windows Phone Advent Calendar 2011
• Windows Azure Advent Calendar jp: 2011
• WordPress Advent Calendar 2011
• カーネル／VM Advent Calendar
• ターミナルマルチプレクサ Advent Calendar 2011
• 変態アドベントカレンダー2011

Source: gihyo.jp

Note that most of the links go to the “Call for participation” pages, which probably has the actual URL for the calendar blogs somewhere. Some communities do it in a distributed way, so the authors post their entries on their own blog and the calendar page just links to them as an index.