Rockstar Games have announced that The Ballad of Gay Tony will be released on October 29, 2009. It can be bought on its own or as part of GTA: Episodes from Liberty City, which contains both The Lost and Damned and The Ballad of Gay Tony.
In addition, Rockstar have also released the first official desktop wallpaper featuring some character art. The girl featured in the art is Gracie Ancelotti - the mob daughter that Niko kidnapped during the mission "I'll Take Her".
Links: GTA IV: The Ballad of Gay Tony; GTA: Episodes from Liberty City.