I don't know Lakeman, I have only ordered from Dadant a couple of times.
There are no promo codes listed for the shipping on the flyer they sent me but if you want the 10%discount on their foundation, frames, woodenware and extractors then the promo cold is SUPER SALE but you have to contact the offices in waverly NY, 1-877-532-3268
Chatham VA 1-800-220-8325 and Frankfort KY and order over the phone.
For the shipping it just says Free Shipping on All products December 1-31 (excluding glass containers, backordered items and orders west of the mississippi) I can't find any promo code so maybe when you order it just automatically takes the shipping off but I would contact them anyway and ask.
Maybe you have to do phone orders for that too.
Brushy Mountain has done free shipping every year in December, I got almost all of my equipment by ordering from them in December.
I had their monthly newsletter but deleted it, not sure if it said anything about the free shipping promo they do though.