I happened on this today ON FACEBOOK (second time I clicked, I really need to get my site up and advertise on FB). It's called Appear Here: http://www.appearherenyc.com/ You can enter when you want to pop up and where and it will do a search for you. I really want to experiment with a shop in the East Village but I most definitely can't afford to jump on this. For those of us who are fearing the L -train shutdown, getting a pop up during that time, or perhaps as a collective some of us could share a space, might save our season...I haven't done a thorough search but I sure plan on it!