How it works: Events start at noon each day and last 40 hours, or until the goods are gone. Sales offer apparel, accessories, home items, and kids fashions at up to 80% off. There are also weekly giveaway contests -- a recent one features a two-day golf getaway -- with surprise start times. Members are notified by e-mail, Facebook and Twitter each time a new sale or giveaway starts.
But discounts have a cost: Ideeli fan Sonia Marti, a fashion production coordinator, pays close attention to expected shipping dates, which can be several weeks away. "I don't want to wait for a month and a half to get my order -- especially if it's something seasonal like those summer sandals I only wore twice by the time summer was over," she says.
Secret strategy: To get an edge on the competition, shoppers can log on at 10 a.m. and browse each sale. You can also buy your way into a head start: "First row" members, who pay $7 a month, can start shopping an hour before everyone else.
What you can snag: A little bit of everything, including Betsey Johnson, Marc by Marc Jacobs, Nicole Miller, Max Mara, Jessica Simpson, Pucci, Sony Music, Furla Handbags, Calvin Klein Home, Cuisinart and LeSportsac luggage.
Ultimate score: The Baby Twin Espresso Maker (pictured), available now, for $475, regularly $699.