TheSchoolLibrary.com
Ask An Expert:
 
Dr. Bob's Interesting Science Stuff  www.frontiernet.net/~docbob/science.htm
A great place for science and technology questions!  Read the previously-answered questions first since your particular question may already have been answered.
The Center for Innovation in Engineering and Science Education
Ask an Expert Site
     www.ciese.org/askanexpert.html
Ask a science expert your question about space and astronomy, biology and life sciences, physics, oceanography, geology, weather, medicine, or health. Sponsor: Stevens Institute of Technology.
Ask Dr. Dig        www.digonsite.com/drdig/
Archeology questions answered here by an Egyptologist/author.
LibrarySpot Ask An Expert    http://www.libraryspot.com/askanexpert.htm Find links to web services connecting inquiring minds to thousands of experts in various subjects.  For general homework help, try LibrarySpot's homework site www.HomeworkSpot.com
 
A note about "Ask An Expert" services:  Before you ask a busy expert to spend time on your question, be sure you have tried to find as much information as you can on your own, or with the help of your librarian.  Write your message clearly, explaining what you are working on and what you need to know. And, plan ahead to allow enough time for the expert to reply to your message before your report or project is due. 

updated 2 Sept. 2012