http://www.factmonster.com/
An informative site for kids as part of an informative and entertaining site for everyone:
http://www.infoplease.com/
Not only information about USA.
Do you know Most Corrupt Countries in the World
Do you need a Conversion Calculator
Do you like Crossword
Ever heard about Quidnunkis
.
graylox who considers emigration to Fattest Countries in the World