The Blue Seed manga series exists in eighteen loose issues or in two volumes and was published by Bamboo Comics. Volume I was released in March of 1995 and Volume II was released in December of 1995. The second volume also includes the short story "Dragonfly."
Visit the gallery for a collection of some of my favorite scenes as well as full page scans of the entire first volume.
Selene Scans has translated the entire series and it is available to the public through their IRC channel or at the gallery. There are also text translations for each volume with pagination.
Four film comics were released to compliment the Blue Seed anime. The animanga consist of cels with text bubbles added. The quality of these is, in my opinion, not so good. They do, however, contain character sketches and other little bits of interest. Scans from volumes one and two can be found in the gallery.
Yonkoma Gekijo is a parody book released by Take Shobo. It consists mostly of silly four-panel omake strips by various artists, but it also contains a pin-up, character sketches, and some really adorable SD drawings. You can find scans in the gallery.