Have there been any Metroid comics/manga, tv shows, or anything?
A 5-part Super Metroid comic, by Benimaru Itoh, ran in Nintendo Power magazine from issues 57-61. These can be found here on the MDb. There were some Super Metroid comic strips in the Japanese manga digest Shounen Oh Game Comic, which can also be found here on the site. Chances are, there are more similar Metroid manga floating around in Japan. As for TV appearances, the Mother Brain was the main villain on the cartoon show Captain N, a show based on Nintendo games, which also featured Mega Man, Pit and the Eggplant Wizard from Kid Icarus, King Hippo from Punch-Out!!, and a waaayyy off-character Simon Belmont from Castlevania, among others. I have heard from a couple sources that ONE episode actually had Samus as a guest star, but nobody has come through with a tape of the episode for me yet. There was also a Captain N comic book published by Valiant, and a few issues of that featured Samus as well.