The Lego City and Lego Friends Advent Calendars are 15% off on Yoyo.com with the code LEGO15 if you buy two lego items included in the promotion. So, you can pick up two advent calendars or one calendar and one other lego set. Some of the other lego sets are already on sale and become good deals with the 15% off promotion.
This isn't an amazing deal, but discounts on these sets are rare and if you find something better you can always return for free.