Battle for Wesnoth - A free turn based strategy game, available for different operating systems (I play on Linux)
Begin 2 - A Tactical Starship Simulation (o/ one step above text-gaming games :p )
Castle of the Winds - an old pc game, still good for a laugh
Conquer Club - A browser based version of Risk.
Cybernations - An online nation simulation game
Imanewbie - An online cartoon site based around Ultima Online (among other things)
Legend Online - A free-to-play Ragnarok Online server
Lexulous - An online scrabble game
Nationstates - Another online nation simulation game, if you start playing look up the nation "The Yi Ta", that's me
Risk - A good, free to download Risk game
TF2 Achievement Generator - Create your own TF2 style achievements
Wireplay - A game service provider that hosts several games, I've played the Ultima Online, Freelancer and Day of Defeat servers (can still be found on DoD, usually the popular maps server)