Netcraft (http://www.netcraft.com/) lets you look up information about web servers; they try to
analyse the headers of responses and other publically-available
information to figure out what web server and OS a site is running.
They can also provide uptime graphs. Useful for `this web
site is cruddy; I wonder if they're running IIS' kinds of questions
when you're too lazy to telnet to port 80 yourself. :-)
CIA World Factbook has background material prepared by the CIA on all the countries
of the world. The material in the factbook itself is in the
public domain (although the official seal of the CIA by law may
not be copied without permission). There's also a
Judaism 101 site at
http://www.jewfaq.org/ is a good place for goyim like me to go to look up what a particular
Jewish holiday commemorates or what to expect at a Passover seder
(although it's got a lot more information than that).