The Dead Movies

I am a fan of George Romero's Dead movies:

Night of the Living Dead [1968]
Dawn of the Dead [1978]
Day of the Dead [1985]
Land of the Dead [2005]

Diary of the Dead, for release in 2007, is a 5th, but not a sequel to Land of the Dead, as it takes place at the during the initial outbreak of the zombies that occurred in Night of the Living Dead.

Remakes of these movies by other directors:

Night of the Living Dead [1990]
Dawn of the Dead [2004]
Night of the Living Dead 3D [2006]
Day of the Dead [2007]

And then of course there's Shaun of the Dead [2004], a spoof of the above, not by George Romero.  See also Night of the Living Bread [1990].

Wikipedia has a good explanation of which are Romero movies, which are Russo movies, and which are non-Romero "sequels" and related and unrelated movies, such as unofficial non-Romero non-Russo sequels Day of the Dead 2: Contagium and Zombi 2.

The original Night of the Living Dead was co-written by George Romero and John Russo.  Romero sequels are "Dead" movies and Russo sequels are "Living Dead" movies.