I don't really follow much manga as it's never been my thing; but I do follow Rosario and Vampire, Claymore, Sankarea, Dance in the Vampire Bund and Yumeki Merry.
These are all series where I saw the anime first, and kinda just fancied being able to get the proper ending.
Rosario is a lot better than the anime though, conversely Claymore's kinda dragging now and I think I probably prefered the anime.