You probably know the flash sale site Gilt City. They're having a warehouse sale in San Francisco (1290 Sutter Street) on May 18, featuring designer brands, including men's and women's fashions, home accessories, kids goods and more. Prices are up to 90% off retail.
Sadly, you have to pay to enter! Cost is $10, but you do get some drinks (prosecco, vodka and coconut water - all designer of course!) and snacks with that, plus live music to get you in the mood, and a photo booth. Also sadly (or not) - you can't bring the kids. But you'll only get entrance for two hours, so babysitting (or spouse sitting) shouldn't set you back much. And don't forget your credit card. Your cash is no good with them.
Get tickets ahead of time, and choose mid-morning, afternoon or late afternoon shopping. Let me know what you buy!