Until October 14, Barnes and Noble online is offering BOGO 50% off select educational toys including LEGO. Some sets like LEGO Friends Advent Calendar, LEGO City Star Wars Advent Calendar and LEGO Star Wars Droid Gunship qualify for stacking with coupon code BNFRIENDS which gives you an additional 20% off (on top of BOGO).
Thanks to brixter and gabriellee11 for the tip.