Marvel Digital Comics, the online arm of Marvel Entertainment, is starting two titles, spinoffs of big-budget Marvel films. “Iron Man: Fast Friends” will focus on the relationship between Tony Stark, the man behind the iron armor, and Jim Rhodes, who comic fans know eventually becomes War Machine, a superhero in his own right. “Incredible Hulk: The Fury Files” will follow Nick Fury (played by Samuel L. Jackson) a cameo appearance in the “Iron Man” movie) as he investigates the angry green monster that Bruce Banner becomes. The series are both weekly. Iron Man will begin on Wednesday; the Hulk will begin on Oct. 8.