LivingSocial, already one of the most popular applications on Facebook, is expanding its group-coupon Deals applications to include New York City following its successful launch for Washington, D.C.

The app gives users a chance to get one great deal per day on restaurants, tickets, hotels and more. Discounts are generally 50% or more, with the potential for your deal to be free if you convince enough of your friends to purchase it through links on Facebook and other social networks. Coupons are limited, so you and your friends need to act on the deals before others do. Today’s New York deal, for example, is for 50 percent off at Cooper’s Tavern.

“The pilot program has been really popular in Washington D.C., so we’re excited about launching in New York City, and eventually nationwide,” says Tim O’Shaughnessy, CEO and co-founder of LivingSocial. “Who doesn’t want a killer deal on luxury spa treatments or tickets to a game?  That’s why people are spreading the word to friends on Facebook and Twitter, so the program builds incredible buzz for our merchant partners. Additionally, our merchants get great branding opportunities and reach hundreds of thousands of local consumers by simply participating in the program.”

Merchants not only get the publicity from being the featured deal, there is also some built-in assurance that the deal will help rather than hurt business. As a group-coupon program, there must be a certain number of coupons purchased before the deal becomes valid. This ensures that merchants will see significant revenue for any deals they process; otherwise, they could get stuck processing a few individuals’ deals, which might not make enough to be worthwhile for some businesses.

The New York City expansion is only the first of many. Look for it to open up in Boston in the near future, and in other cities in the coming months.