The Chelsea Collaborative will present its “Unsung Heroes of 2012” at its annual holiday gala on Dec. 7 from 6 p.m. to midnight at the Holiday Inn in Somerville. This year’s unsung heroes include Chelsea City Manager Jay Ash; the Metro North Regional Employment Board; the Foley Hoag law firm; and Two Sisters and a Wife Foundation. The collaborative is a nonprofit agency located at 318 Broadway. In addition to celebrating Chelsea’s unsung heroes, the annual gala raises money for the group’s work, which includes a summer youth employment program and a Green Space Committee that focuses on environmental projects. For more information, call the collaborative at 617-889-6080.