Halo will be seven years old tomorrow (the original game was released Nov. 15, 2001). It started as an experiment. Could Bungie, a company that made shooters for the Macintosh, make a shooter for Microsoft's new console system? It turned into a juggernaut.
Bungie was acquired by Microsoft and then last year split from them. Microsoft retains the rights to all things Halo, but Bungie is still in the picture and the series is still going strong. Bungie is working on Halo 3: Recon, a fall 2009 expansion that adds a new campaign with a new hero, presumably set on Earth while the Covenant are invading. There have been five Halo novels as well as a graphic novel. A sixth novel subtitled The Cole Protocol is due out on November 25th.