The following list represents ten of the best online resources that children or parents can use to ask science questions, or search science questions that are already answered. These sites are either moderated by science experts that personally answer questions themselves, or they are supported by visitors that have a science background and volunteer to answer student questions. In either case, these sites can really help when you just don't know where else to turn to help your child with their science homework.
Bill Beaty created this website devoted to electricity in 1999. Ever since then, he's been personally answering questions related to the science of electricity.

Ask Electricity Questions
The site itself has a bit of an outdated design, but you can find questions that Bill has answered archived all the way back to 1999. If you don't find the information you're looking for, go ahead and post your own question. Bill will answer it personally!
Alfy is a fantastic resource, not only for questions but also as a fun place for kids to spend time while learning. At Alfy, kids can play games, answer polls, have conversations on the forums, and even find some interesting arts & crafts.

Alfy Questions and Answers
Alfy is probably also one of the easiest places to get science questions answered. On the "Answers" page, there's a field where you can quickly post your question. Visitors to the site that know the answer can reply.
Like Alfy, at WebAnswers kids can post questions and get answers from people that are registered to provide answers. There are many categories at WebAnswers, but the "Science & Math" category covers just about every branch of science you could imagine.

Science & Math at WebAnswers
At WebAnswers, you can either click on one of the science categories and search for an answer to your question, or just click on the "Ask" tab and post your own question.
The tagline at this New Scientist page called "The Last Word" is "The science of everyday things." It's actually a page for anyone to post their science questions, but it's especially useful for kids that are curious about some of those fundamental science questions.

The Last Word
Anyone can post questions, but you do need to sign up for a membership, so kids will need to ask their parents for permission before posting any questions.
AllExperts is a popular question and answer site that features registered "experts" who are ready to answer any questions posed on the site. Any site that has experts makes for excellent resources to get science questions answered.

Ask Experts at AllExperts
The process at AllExperts is a little different. The site encourages visitors to first browser through answers published by experts. If the answer isn't already there, then you should ask a specific expert directly.
The "Ask a Scientist" site is offered by none other than Argonne National Laboratory. It is a public service supported by the Department of Education and the Department of Energy.

Ask a Scientist
The website reportedly receives over ten million hits a month, with a great deal of questions submitted by visitors. Because of this, you may often find that the site is off-line. However, there's an extensive archive area that you can use to search for answers to your questions.
The Mad Science Network is a fantastic resource for kids that love science. Not only will you find an archive of over 36,000 answers to past questions that have already been answered, but there's also an "Ask-A-Scientist" section for more questions.

Ask-A-Scientist and More
In addition to Ask-A-Scientist, students can test their knowledge with the knowledge generator, try fun experiments at "MAD Labs" or visit the MadSci Library for help with science research.
TutorNext is more commonly known as a resource for obtaining online tutors. While the tutor service isn't free, the "Answers" section of the website is.

Ask Questions on TutorNext
In the Answers section, you post any science question you like. People are encouraged to answer to earn points and built their credibility as "experts" on the site.
If you can't seem to find any answers from the question & answer sites, InfoPlease may be a good resource to turn to. Like a virtual encyclopedia, it has information on a very wide range of topics kids will encounter in Science class.

The Science Homework Center
The site has a special homework center just for the Sciences where kids can search for the information they need. This is an excellent resource for writing a term paper or doing research for any science project.
Like the other sites above the offer an archive of past answers, How Everything Works has a topics page that lists topics such as airplanes, clocks, roller coasters and much more. This website is focused primarily on Physics.

Past Questions and Answers
At each section, you'll find all of the past questions and answers posed by visitors. If you can't find what you're looking for, click on "Ask a Question" and fill out the form with your own query.
The ability to pose science questions online is a very nice feature for kids, especially when they are stuck and trying to understand especially difficult homework problems.
Sometimes, the level of required scientific knowledge rises above that of parents, so all of these websites provide much-needed help to both the students and parents. They shouldn't be used to answer homework questions, but they are important tools to assist children with understanding difficult or complex scientific ideas.