There are times when you want to know who the head of state / government / power is in a particular jurisdiction, and for those times Rulers is the site you need. Something like CanLII’s new point-in-time legislation database, Rulers offers a point-in-time database of information about who was in charge here, there and everywhere between 1700 and now.
The site offers you four ways, more or less, to get into the data: an alpha index to the jurisdictions, an index of dates (this only back to 1996) of “relevant events,” an alpha index of everything, and a map keyed to the database. (There’s a small hotlinked map on the front page, but if you’re aiming for something smaller than China, you might want to use the larger map.)
Thus, clicking on Canada reveals that one Stephen Harper, Conservative, born 1959, is Prime Minister and has been since February 6, 2006; that Sir John Thompson was Prime Minister from December 5, 1892 to December 12, 1894; that Henry Petty-Fitzmaurice, Marquess of Lansdowne, was Governor-General between 1883 and 1888; and so on. Names are often hotlinked to mini-biographies, sometimes with a photograph included. There’s more here, but you’ll find it easily enough by following your nose.
It would seem that the site is kept more or less up to date: the latest entry was made at the end of January, 2009.
All in all, a handy reference tool to have in your bookmarks.