Ask the Experts
There are generally two types of ask an expert sites. First, there are the specialized sites, maintained by experts who can supply detailed and specific information in one, well-defined field. The second type are the generalist sites, maintained by experts in different fields that can give you the answer to questions in all kind of fields. Usually these "ask an expert" sites will return an answer within 24 hours.
The following are suggestions for popular “Ask the Experts” sites:
Ask a Librarian
An online reference service from the Library of Congress
Experts Exchange
Thousands of experts answer technical questions. The focus is on computer
science.
The Educator's Reference Desk
If you got a question on any education topic trained person experts, will respond
to your question within a day or two with an annotated bibliography of web
sites and journal articles and books on the topic.
CIESE ask an
expert-sites
An extensive overview of specialized ask an expert-sites.
AllExperts.com
The oldest & largest free Q&A service on the Internet. Thousands of
volunteers, including lawyers, doctors, engineers, and scientists, waiting to
answer your questions. All answers are free and most come within a day.
Dmoz: ask-an-expert
Another extensive overview of "ask an expert" sites.)
QuestionPoint
A collaborative project of the Library of Congress and OCLC.
Dr.Math
Mathematics experts.