These are the advent and holiday calendars I found this year:

• 24 ways to impress your friends
• 24 Pull Requests – Giving back little gifts of code for Christmas
• UXmas – An advent calendar for UX folk
• FastMail Advent 2016
• Perl Advent Calendar 2016
• Advent Calendar 2016 by Jens Grochtdreis

There is no Webkrauts Adventskalender this year, but there is a German version of the advent calendar by Jens:

• Adventskalender 2016

If you know any interesting holiday or advent calendars, please post them in the comments.