Sorry if any of these have already been mentioned, I haven't read every post.
http://www.Wikipedia.com - An online encyclopedia that anybody can edit. You might think it be really screwed up if anyone can edit it, but for the most part all edits are closely watched and changed promptly if they're unnecessary/vandalist/false.
http://www.NationMaster.com - Shows you all kinds of interesting statistics for just about every nation on earth. Stuff like richest nation, poorest, most generous, etc.
http://www.IMDB.com - Great website for learning various info about nearly any TV show or movie.
http://www.StraightDope.com - Check the archives. Great info in there, should provide plenty of reading material.
http://www.stuart.iit.edu/students/adamadr/portfolio/artwork.html - Some GB fansite, this guy is a pretty good artist. He's drawn original artwork for a futuristic GB series he's thought up.
http://www.HowStuffWorks.com - Learn how many of the common things you may use or see every day work. This site even tells you how fictional things would theoretically work, like lightsabers and teleporters.
http://rinkworks.com/dialect/ - And last, but not least, a hilarious site you can use to change just about any webpage into redneck speak and other funny dialects. Just type in the URL and the dialect you want, and it'll show you that actual page except with all the words spoken of the particular dialect you chose. Once I've fooled some friends by switching
CNN.com to “Hacker speak” and they actually believed CNN had been hacked. Very funny.