Rulers. The complete list of all rulers of this small chunk of rock dating back to 1700 or so. The Internet at its finest!
This site contains lists of heads of state and heads of government (and, in certain cases, de facto leaders not occupying either of those formal positions) of all countries and territories, going back to about 1700 in most cases. Also included are the subdivisions of various countries (the links are at the bottom of the respective country entries), as well as a selection of international organizations. Recent foreign ministers of all countries are listed separately.