Use coupon code "IAMBACK" at Boxed.com to get $3 off your purchase. I've been able to use it more than once.
I'm not sure when it expires. It does NOT work with the $15 new account offer. But it would work for an existing account and also works with Ibotta.
I was also able to get it to stack with the 10% off code "DONTRUNOUT" (which I found in this thread: http://slickdeals.net/f/9194827-boxed-com-10-off-coupon)
The Amex offer expired this past weekend, but if you have Boxed Cash Rewards left from an order you can stack them with the codes. That should give you about $6.50 off a $19.99 order.
There is also a Halloween Goodie Box you can add to your order for free, while supplies last. It includes:
-1 Pumpkin Trick or Treat bag
-2 Spider Tattoos
-1 Bag of Cobwebs
-2-3 pieces of Hershey's Miniature Chocolates
You can also add two free samples to your order. If they are in stock, maybe you will get them. Maybe not. Right now they have AAA batteries and a Fig Bar.