I will list a few sites that are friendly to me and or have consumed hours and hours of my life, shoot me an email if you have anything to add to this list.
An online web comic I enjoy is http://xkcd.com/ I imagine most here at IGX will be able to relate.
a4q is a site run by a nice guy named Tony. It has a small loyal community and is a fun game. It is in a sentence a4q is mutiplayer go on steroids. Definantly wort a try.
I got hooked on the board game Diplomacy back in high school and have found a site online to play it by email: Diplomacy 2000 This is the only military board game I know that has no chance or roll of the die involved in gameplay. It mocks ww1 style of combat and diplomacy, it is a battle of wits between seven players. I warn you this is not a thing to take likely though, the game I am currently playing has been going on for over 6 months with one turn adjudicating every 2 weeks. One of my favorite games for sure though.
This last game I am at odds with. It is addicive and time consuming with no doubt but I have a place in my heart for this game and its txt interface. Astro Empires is the game I played when Intergalactics was down and I had no space strategy fix, it is a great game... if you have the time and don't require nice graphics.