One website is WikiAnswers, which is what you are looking at right now.
www.math.com
elearning.com
This one could be one
Yes, there are other websites that answer questions.
There are several websites that have test questions for the MOH (Ministry of Health) test for nurses. Practices tests and study guides are also available on these websites.
cha cha ask.com and of course wikki answers
Nobody knows. If you get the Driver Study Guide they have some sample questions over each chapter. There are some websites that you can get on also to take practice tests but those aren't going to be the exact questions on the test. :)
You can use Google or Bing search engines. Yahoo also takes user questions. And there are some pay websites.
I don't think this counts but Wikipedia may have the answers to your questions...
Diagnosis.com
This website has one. See related questions.
Many websites have user-compiled lists of general knowledge questions. There are also many books containing such lists, such as "Pub Quiz" compilations and other similar books. Some examples of websites include "Challenge the Brain" and a blog called "General Knowledge Questions and Answers"