Here are a few links that I've had stored for quite a while in my bookmarks.
Two are schedule grids (so you don't have to buy TV Guides or Satellite Guides). These are TV Guide and Zap2it. Both are really useful. I've been using Zap2it for the last few years. TV Guide is just as good, if not more well known.
TV Now has a theme search feature with lists movies for a particular theme. And it tells you the scheduled times and stations for them, usually within a month's time. You can get listings based on actor, actress, director, Sci-Fi, Horror, G-Rated, Martial Arts, Musicals, Foreign, Letterbox, Classic Comedy, Classic Mystery, Classic Western, 4-Star, Film Noir, Detective, World War II and Silent films. Very useful if you just want to watch specific types of films.
TV Tome has what would be the most comprehensive online guide to almost every show ever broadcast. Great resource. Includes episode guides and character info, as well as details about the original airdates. Here are a some samples: The Avengers, The Prisoner, Twilight Zone, Aeon Flux, La Femme Nikita, Alias, The Saint, Buffy the Vampire Slayer, Charlies Angels, Starsky and Hutch, Firefly, Star Trek, Batman, Mission Impossible, Moonlighting, Outer Limits, Alfred Hitchcock Presents.
And for individual channels, here are the sites for BBC America, The Sci-Fi Channel, Starz Action Channel, Starz Mystery Channel, Sundance Channel, and The Independent Film Channel.