St. Mango's, also known as St. Manga's, appears to be some sort Wizarding rehabilitation facility. It may be based on St. Mungo's from the books.
St. Mango's is a place to get treatment for Voldemortserum addiction - although Professor Sinister refused to go get treatment. St. Mango's also treats "pedofiles". At one point, there are plans to send Snap and Loopin there after they videotape Enoby in the bath.