At Costco, take $10 off orders of $100 or more when you fill out this form and then share the offer on Facebook, Twitter, or via email. (Once you share the offer, you will be given a unique coupon code.) Shipping starts at around $5, but many items sitewide receive free shipping. That's tied with our mention from three weeks ago and a rare sitwide dollar-off discount from Costco.
Note that this coupon can only be used online at Costco.com.