Excellent, detailed article on how Microsoft calculate TrueSkill - an algorithm for matching you to players about in your skill level. This is what is used every time you hit "game with strangers" on an XBL title, basically. Fascinating, detailed, not too challenging if you take it slow/steady - and the implementation is on github...

RubyQuiz on A* pathfinding.

Technically hardcore, dense paper explaining how the Dungeon Siege environment was constructed without a loading screen. Word of the day: "frustrum". Interesting stuff in here. Now, how to apply it?