While Sega has annouced that they will no longer be supporting the Dreamcast it is still possible to get the Dreamcast manual, VMU Manual and the manual for a number of dreamcast games from the sega website.
If you happen to need the manuals for Phantasy Star or Samba de Amigo, Jet Grind Radio or some other game go there and download while you still can. They are on the two lists at the bottom. Some of them are more complete than others but if you are in need you can at least get SOMETHING.
I just downloaded a Bomberman Online manual that I needed for my rental copy I picked up a few months ago.