Top question and answer site list

http://answers.yahoo.com/
http://www.ask.com/
http://wiki.answers.com/
http://aolanswers.com/
http://stackexchange.com/
http://mathoverflow.net/
http://www.linkedin.com/answers
http://www.mahalo.com/
http://www.fixya.com/
http://www.fluther.com/
http://askville.amazon.com/Index.do
http://www.answerbag.com/
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http://able2know.org/
http://www.avvo.com/
http://www.girlsaskguys.com/
https://www.healthtap.com/
http://www.funadvice.com/
http://www.answerhighway.com/
http://www.whanswers.com