I might as well say it, seeing as no one else has. Animations are known as Anime, Manga is the name for comics. It's confused in the west by one of the major distributors of Anime calling themselves Manga as a company name.
As for what's worth watching - well, one way or another, pretty much all of them. Like beer, or porn, there's only less good, not bad Anime.
Anything from Studio Ghibli is pretty near the top, and Ghost in the shell movies and series are all excellent, but a list of good Anime would be vast.
Oh, and make sure you watch them with subs, otherwise the obnoxious American dubs will reduce these great works to nothing more than inept episodes of Scooby Do, or any of the other junk by-the-numbers kid's animations.
RegarRAB
Mark