"Sutekh the Destroyer," also called "Set," "The Typhonian Beast," and "Satan," appeared as a bad guy in Doctor Who and the Pyramids of Mars. They got all the evil connections right, and they even got Seth's attitude right, except that Sutekh's race is listed as "Osirian" (huh?). They make up for it by letting the Big Red Dude actually win a fight against Horus the Younger, for once!
Mahmoud El Arch is an Egyptian composer who makes music for movies and video games. Awesome gig, right? One of his works based on ancient Egyptian mythology is a piano piece called "March of Seth."
Kayla Pierson made a stop-motion version of the legend of Seth murdering Osiris for a class at the University of Montana. It tells the story from the Plutarch version (ca. 100CE) which is a little different—and a lot bloodier—than the ancient Egyptian versions). Unfortunately, since Horus always wins, many people believe this is the only version of the story.
The video game Tomb Raider 4 includes a movie about Set. And yet again, Horus wins!
Seth appears as a bad guy/bad god in a number of different books and TV shows and movies, including the Kane Chronicles books by Rick Riordan, where he is the main villain in The Red Pyramid.