Not a terribly exciting promotion, but if you were thinking about purchasing something off of Gilt and haven't yet become a member, sign up now and you'll receive 1,500 Mileage Plus or OnePass miles after your first purchase. In addition, you'll earn 5 miles per dollar spent on Gilt Groupe within the first 6 months of registration. Your miles should be credited within 6-8 weeks after the first purchase. There is no fee for registering or becoming a member.
Gilt Groupe consists of a number of different portals, including the original Gilt website that features limited-time offers on designer clothing. They've also expanded to include Gilt City, which mimics what Groupon does for local deals, Jetsetter, which offers travel deals, and Gilt Taste, featuring fine wines and high-end foods.
You may have to do some digging on the website, but there are often times fairly inexpensive items for sale. The cheapest item I've found so far is a sushi mat for only $2.95 plus $5.95 shipping, which comes to a total of $8.90. Just go to the Gilt Taste section, under the "Equipment" tab, select "Accessories". Then just sort by price and it should be the first item listed.
EDIT 4/11/2012: I noticed today that this offer has been updated with a new requirement that the initial purchase must be at least $50, exclusive of taxes and shipping. This makes it slightly less worthwhile. But if you are already planning on signing up for Gilt and making a purchase over $50, then it makes sense to take advantage of this offer.