A resource I've drawn upon in the past is this page, from the French Historical Service of Defense. It includes well over a thousand high-res plans for a large number of ships and equipment. It ranges from 1st rate lineships to small cutters, on through early sidewheel steam vessels and forward into WWI-era battleships; all primarily French, of course.
http://translate.googleusercontent.com/translate_c?depth=1&hl=en&rurl=translate.google.com&tl=en&u=http://archive.is/Pu62&usg=ALkJrhjis22A4AKm12zXcyLRKvEjt3V1wg