have you tried googling lego couon code? I usually get taken to a site named retail me not (I think that's the name). I don't normally see legos on sale though. One thing I have just discovered is there is a VIP legos card. Spend $100 and get $5 coupon. Not much, but it's the best I've found so far. Good luck!
Actually, through Monday, the 10% comes off automatically - free shipping for $49 and up, and a free holiday set for an order of $99 or more. DS was saving up to buy some, and he pooled his $50 with the birthday money from my Mom; he picked out 2 3-in-1 sets, and got the holiday set...we also got 2 HP-themed keychains, and a Duplo alphabet set for DD - total was $146!
Even better, when I called to make sure the order was in process, because I hadn't received an e-mail, they said they'll send DS a $5 gift card because it's his birthday. We should also be getting at least $10 in rewards now so we'll go to the store in January and he and DD can each pick out something small.