I came across the Gamasutra site (http://www.gamasutra.com/) through a game design group that I am looking to be part of. More specifically I was pointed at this article "A Few Remarks on Creative Play" by Ernest Adams (http://www.gamasutra.com/features/20050429/adams_01.shtml). Ernest gives a very approachable look at gameplay types which divert from the competitive styling that most games follow to look at creative modes.
I also enjoyed their article on Zork (http://www.gamasutra.com/view/feature/1499/the_history_of_zork.php) - blimey this is bringing back distant and fond memories of playing this on one or other of the mainframes at UNE many moons ago. I remember my cousin and his friends spending long long hours in teams trying to solve the puzzles that were set before them by this little legend of a game.