It’s a bit late, perhaps, but here’s a list of some of the advent calendars for 2014.
- QEMU
- Perl 6 Advent Calendar
- Catalyst
- Java Advent Calendar
- Gopher Academy 2014 Calendar
- Free Font Advent Calendar
- 24 Ways to Impress Your Friends
A huge list of Advent Calendars can be found at Qiita.
A “Planet” aggregator for Advent Calendars is hosted by Len Jaffe.