Today's site is not exactly for kid but teens and adults can use the link to browse for general knowledge.
Wise Geek is one of the sites, which is created by a team of writers and editors (over 50 contributors) to provide clear and concise answers to common questions. Access to the web site is FREE.
Who is behind all this effort, you can check at this link: Who is Wise Geek
Check the FAQ section for more information.
There is a list of questions at the home page, but if you don't get the answers to your questions, then just write your question at a search box and click it. Right now they have more than 19,200 articles.
Link to the site: wiseGEEK: clear answers for common questions