Popular check-in application Foursquare announced today on its blog that as of last week it has more than half a million businesses signed up and offering specials.

Businesses looking to take advantage of customers using Foursquare to check in to their locations can sign up for a merchant account. Once they do so, they can offer specials, update venue information and gain useful insights on check-in data, such as popular days and times. Best of all, it’s free.

Foursquare spotlights several specials that are currently running, including one from Radisson Hotels that allows guests to check out 2 hours later than normal. Also, McDonald’s is offering a free beverage with the purchase of a meal to people who check in with Foursquare.

Foursquare has been busy the past couple months. The company recently closed a $50 million round of funding and reached a milestone of more than 10 million users.

Foursquare, founded in 2009 and based in New York City, has raised more than $71.4 million in funding to date. It currently has more than 70 employees in its home town and an engineering office in San Francisco.

VB’s research team is studying mobile user acquisition: Chime in here, and we’ll share the results.