Comcast Corp. and Metro-Goldwyn-Mayer Inc. said Tuesday they are teaming up to introduce a video-on-demand channel featuring action movies and TV shows. Comcast, the country's largest cable operator, already has a hit with another genre-specific VOD channel and Web site, FEARnet, which features horror movies and thrillers, in collaboration with Lionsgate and Sony Pictures Television. FEARnet is also available on mobile phones.